From a5365d829219677b66667c40099102becc7a3644 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tu=C4=9F=C3=A7e=20K=C3=BC=C3=A7=C3=BCko=C4=9Flu?=
 <tugcekucukoglu.860@gmail.com>
Date: Fri, 16 Jul 2021 12:39:45 +0300
Subject: [PATCH] Fixed #692 - VirtualScroller Component

---
 api-generator/components/virtualscroller.js   | 124 +++
 src/assets/menu/menu.json                     |   5 +
 .../virtualscroller/VirtualScroller.d.ts      |  27 +
 .../virtualscroller/VirtualScroller.vue       | 545 ++++++++++++
 src/components/virtualscroller/package.json   |   9 +
 src/main.js                                   |   2 +
 src/router/index.js                           |   5 +
 src/views/liveeditor/LiveEditor.vue           |   2 +
 .../virtualscroller/VirtualScrollerDemo.vue   | 243 ++++++
 .../virtualscroller/VirtualScrollerDoc.vue    | 824 ++++++++++++++++++
 10 files changed, 1786 insertions(+)
 create mode 100644 api-generator/components/virtualscroller.js
 create mode 100644 src/components/virtualscroller/VirtualScroller.d.ts
 create mode 100644 src/components/virtualscroller/VirtualScroller.vue
 create mode 100644 src/components/virtualscroller/package.json
 create mode 100644 src/views/virtualscroller/VirtualScrollerDemo.vue
 create mode 100644 src/views/virtualscroller/VirtualScrollerDoc.vue

diff --git a/api-generator/components/virtualscroller.js b/api-generator/components/virtualscroller.js
new file mode 100644
index 000000000..143fd2f33
--- /dev/null
+++ b/api-generator/components/virtualscroller.js
@@ -0,0 +1,124 @@
+const VirtualScrollerProps = [
+    {
+        name: "items",
+        type: "array",
+        default: "null",
+        description: "An array of objects to display."
+    },
+    {
+        name: "itemSize",
+        type: "number|array",
+        default: "null",
+        description: "The height/width of item according to orientation."
+    },
+    {
+        name: "scrollHeight",
+        type: "string",
+        default: "null",
+        description: "Height of the scroll viewport."
+    },
+    {
+        name: "scrollWidth",
+        type: "string",
+        default: "null",
+        description: "Width of the scroll viewport."
+    },
+    {
+        name: "orientation",
+        type: "string",
+        default: "vertical",
+        description: "The orientation of scrollbar, valid values are 'vertical', 'horizontal' and 'both'."
+    },
+    {
+        name: "numToleratedItems",
+        type: "number",
+        default: "null",
+        description: "Determines how many additional elements to add to the DOM outside of the view. According to the scrolls made up and down, extra items are added in a certain algorithm in the form of multiples of this number. Default value is half the number of items shown in the view."
+    },
+    {
+        name: "delay",
+        type: "number",
+        default: "0",
+        description: "Delay in scroll before new data is loaded."
+    },
+    {
+        name: "lazy",
+        type: "boolean",
+        default: "false",
+        description: "Defines if data is loaded and interacted with in lazy manner."
+    },
+    {
+        name: "showLoader",
+        type: "boolean",
+        default: "false",
+        description: "Whether to show loader."
+    },
+    {
+        name: "style",
+        type: "any",
+        default: "null",
+        description: "Inline style of the component."
+    },
+    {
+        name: "class",
+        type: "string",
+        default: "null",
+        description: "Style class of the component."
+    }
+];
+
+const VirtualScrollerEvents = [
+    {
+        name: "scroll-index-change",
+        description: "Callback to invoke when scroll position and item's range in view changes.",
+        arguments: [
+            {
+                name: "event.first",
+                type: "number",
+                description: "First index of the new data range to be loaded."
+            },
+            {
+                name: "event.last",
+                type: "number",
+                description: "Last index of the new data range to be loaded."
+            }
+        ]
+    },
+    {
+        name: "lazy-load",
+        description: "Callback to invoke in lazy mode to load new data.",
+        arguments: [
+            {
+                name: "event.first",
+                type: "number",
+                description: "First index of the new data range to be loaded."
+            },
+            {
+                name: "event.last",
+                type: "number",
+                description: "Last index of the new data range to be loaded."
+            }
+        ]
+    }
+];
+
+const VirtualScrollerSlots = [
+    {
+        name: "item",
+        description: "Content for the item"
+    },
+    {
+        name: "loader",
+        description: "Custom content for the loader items"
+    }
+];
+
+module.exports = {
+    virtualscroller: {
+        name: "VirtualScroller",
+        description: "VirtualScroller is a performant approach to handle huge data efficiently.",
+        props: VirtualScrollerProps,
+        events: VirtualScrollerEvents,
+        slots: VirtualScrollerSlots
+    }
+};
\ No newline at end of file
diff --git a/src/assets/menu/menu.json b/src/assets/menu/menu.json
index bda582c81..096dafd16 100644
--- a/src/assets/menu/menu.json
+++ b/src/assets/menu/menu.json
@@ -406,6 +406,11 @@
                     "name": "DataView",
                     "to": "/dataview"
                 },
+                {
+                    "name": "VirtualScroller",
+                    "to": "/virtualscroller",
+                    "badge": "New"
+                },
                 {
                     "name": "FilterService",
                     "to": "/filterservice"
diff --git a/src/components/virtualscroller/VirtualScroller.d.ts b/src/components/virtualscroller/VirtualScroller.d.ts
new file mode 100644
index 000000000..dcebabbf0
--- /dev/null
+++ b/src/components/virtualscroller/VirtualScroller.d.ts
@@ -0,0 +1,27 @@
+import { VNode } from 'vue';
+
+interface VirtualScrollerProps {
+    items?: any[]|any[][];
+    itemSize?: number|any[];
+    scrollHeight?: string;
+    scrollWidth?: string;
+    orientation?: string;
+    numToleratedItems?: number;
+    delay?: number;
+    lazy?: boolean;
+    showLoader?: boolean;
+    loading?: boolean;
+    style?: any;
+    class?: string;
+}
+
+declare class VirtualScroller {
+    $props: VirtualScrollerProps;
+    $emit(eventName: 'update:numToleratedItems', value: number): this;
+    $emit(eventName: 'scroll-index-change', value: { first: number, last: number }): this;
+    $emit(eventName: 'lazy-load', value: { first: number, last: number }): this;
+    $slots: { 
+        items: VNode[];
+        loader: VNode[];
+    }
+}
\ No newline at end of file
diff --git a/src/components/virtualscroller/VirtualScroller.vue b/src/components/virtualscroller/VirtualScroller.vue
new file mode 100644
index 000000000..e40b2cf31
--- /dev/null
+++ b/src/components/virtualscroller/VirtualScroller.vue
@@ -0,0 +1,545 @@
+<template>
+    <div :ref="elementRef" :class="containerClass" :style="style" @scroll="onScroll">
+        <div :ref="contentRef" class="p-virtualscroller-content">
+            <template v-for="(item, index) of renderItems" :key="index">
+                <slot name="item" :item="item" :options="getOptions(index)"></slot>
+            </template>
+        </div>
+        <div :ref="spacerRef" class="p-virtualscroller-spacer"></div>
+        <div :class="loaderClass" v-if="d_loading">
+            <template v-for="(loadItem, index) of loaderArr" :key="index">
+                <slot name="loader" :options="getLoaderOptions(index)">
+                    <i class="p-virtualscroller-loading-icon pi pi-spinner pi-spin"></i>
+                </slot>
+            </template>
+        </div>
+    </div>
+</template>
+
+<script>
+export default {
+    name: 'VirtualScroller',
+    emits: ['update:numToleratedItems', 'scroll-index-change', 'lazy-load'],
+    props: {
+        items: null,
+        itemSize: {
+            type: [Number,Array],
+            default: null
+        },
+        scrollHeight: null,
+        scrollWidth: null,
+        orientation: {
+            type: String,
+            default: 'vertical'
+        },
+        numToleratedItems: {
+            type: Number,
+            default: null
+        },
+        delay: {
+            type: Number,
+            default: 0
+        },
+        lazy: {
+            type: Boolean,
+            default: false
+        },
+        showLoader: {
+            type: Boolean,
+            default: false
+        },
+        loading: {
+            type: Boolean,
+            default: false
+        },
+        style: null,
+        class: null
+    },
+    data() {
+        return {
+            first: this.isBoth() ? { rows: 0, cols: 0 } : 0,
+            last: this.isBoth() ? { rows: 0, cols: 0 } : 0,
+            numItemsInViewport: this.isBoth() ? { rows: 0, cols: 0 } : 0,
+            lastScrollPos: this.isBoth() ? { top: 0, left: 0 } : 0,
+            d_numToleratedItems: this.numToleratedItems,
+            d_loading: this.loading,
+            loaderArr: null
+        }
+    },
+    element: null,
+    content: null,
+    spacer: null,
+    scrollTimeout: null,
+    mounted() {
+        this.$nextTick(function () {
+            this.init();
+        });
+    },
+    watch: {
+        numToleratedItems(newValue) {
+            this.d_numToleratedItems = newValue;
+        },
+        loading(newValue) {
+            this.d_loading = newValue;
+        }
+    },
+    methods: {
+        init() { 
+            this.setSize();
+            this.calculateOptions();
+            this.setSpacerSize();
+        },
+        getLast(last, isCols) {
+            return this.items ? Math.min((isCols ? this.items[0].length : this.items.length), last) : 0;
+        },
+        calculateOptions() {
+            const isBoth = this.isBoth();
+            const isHorizontal = this.isHorizontal();
+            const first = this.first;
+            const itemSize = this.itemSize;
+            const contentPadding = this.getContentPadding();
+            const contentWidth = this.element ? this.element.offsetWidth - contentPadding.left : 0;
+            const contentHeight = this.element ? this.element.offsetHeight - contentPadding.top : 0;
+            const calculateNumItemsInViewport = (_contentSize, _itemSize) => Math.ceil(_contentSize / (_itemSize || _contentSize));
+            const numItemsInViewport = isBoth ?
+                { rows: calculateNumItemsInViewport(contentHeight, itemSize[0]), cols: calculateNumItemsInViewport(contentWidth, itemSize[1]) } :
+                calculateNumItemsInViewport((isHorizontal ? contentWidth : contentHeight), itemSize);
+
+            let numToleratedItems = this.d_numToleratedItems || Math.ceil((isBoth ? numItemsInViewport.rows : numItemsInViewport) / 2);
+            const calculateLast = (_first, _num, _isCols) => this.getLast(_first + _num + ((_first < numToleratedItems ? 2 : 3) * numToleratedItems), _isCols);
+            const last = isBoth ?
+                { rows: calculateLast(first.rows, numItemsInViewport.rows), cols: calculateLast(first.cols, numItemsInViewport.cols, true) } :
+                calculateLast(first, numItemsInViewport);
+
+            this.d_numToleratedItems = numToleratedItems;
+            this.$emit('update:numToleratedItems', this.d_numToleratedItems);
+            this.last = last;
+            this.numItemsInViewport = numItemsInViewport;
+
+            if (this.showLoader) {
+                if (this.$slots && this.$slots.loader) {
+                    this.loaderArr = Array.from({ length: (isBoth ? numItemsInViewport.rows : numItemsInViewport) });
+                }
+                else {
+                    this.loaderArr = Array.from({ length: 1});
+                }
+            }
+
+            if (this.lazy) {
+                this.$emit('lazy-load', { first, last });
+            }
+        },
+        getContentPadding() {
+            if (this.content) {
+                const style = getComputedStyle(this.content);
+                const left = parseInt(parseFloat(style.paddingLeft.slice(0, -2)), 10);
+                const right = parseInt(parseFloat(style.paddingRight.slice(0, -2)), 10);
+                const top = parseInt(parseFloat(style.paddingTop.slice(0, -2)), 10);
+                const bottom = parseInt(parseFloat(style.paddingBottom.slice(0, -2)), 10);
+
+                return { left, right, top, bottom, x: left + right, y: top + bottom };
+            }
+
+            return { left: 0, right: 0, top: 0, bottom: 0, x: 0, y: 0 };
+        },
+        setSize() {
+            if (this.element) {
+                const isBoth = this.isBoth();
+                const isHorizontal = this.isHorizontal();
+                const parentElement = this.element.parentElement;
+                const width = this.scrollWidth || `${(this.element.offsetWidth || parentElement.offsetWidth)}px`;
+                const height = this.scrollHeight || `${(this.element.offsetHeight || parentElement.offsetHeight)}px`;
+                const setProp = (_name, _value) => this.element.style[_name] = _value;
+
+                if (isBoth) {
+                    setProp('height', height);
+                    setProp('width', width);
+                }
+                else {
+                    isHorizontal ? setProp('width', width) : setProp('height', height);
+                }
+            }
+        },
+        setSpacerSize() {
+            const items = this.items;
+
+            if (this.spacer && items) {
+                const isBoth = this.isBoth();
+                const isHorizontal = this.isHorizontal();
+                const itemSize = this.itemSize;
+                const contentPadding = this.getContentPadding();
+                const setProp = (_name, _value, _size, _padding = 0) => this.spacer.style[_name] = (((_value || []).length * _size) + _padding) + 'px';
+
+                if (isBoth) {
+                    setProp('height', items[0], itemSize[0], contentPadding.y);
+                    setProp('width', items[1], itemSize[1], contentPadding.x);
+                }
+                else {
+                    isHorizontal ? setProp('width', items, itemSize, contentPadding.x) : setProp('height', items, itemSize, contentPadding.y);
+                }
+            }
+        },
+        setContentPosition(pos) {
+            if (this.content) {
+                const isBoth = this.isBoth();
+                const isHorizontal = this.isHorizontal();
+                const content = this.content;
+                const first = pos ? pos.first : this.first;
+                const itemSize = this.itemSize;
+                const calculateTranslateVal = (_first, _size) => (_first * _size);
+                const setTransform = (_x = 0, _y = 0) => content.style.transform = `translate3d(${_x}px, ${_y}px, 0)`;
+
+                if (isBoth) {
+                    setTransform(calculateTranslateVal(first.cols, itemSize[1]), calculateTranslateVal(first.rows, itemSize[0]));
+                }
+                else {
+                    const translateVal = calculateTranslateVal(first, itemSize);
+                    isHorizontal ? setTransform(translateVal, 0) : setTransform(0, translateVal);
+                }
+            }
+        },
+        onScrollPositionChange(event) {
+            const target = event.target;
+            const isBoth = this.isBoth();
+            const isHorizontal = this.isHorizontal();
+            const itemSize = this.itemSize;
+            const contentPadding = this.getContentPadding();
+            const calculateScrollPos = (_pos, _padding) => _pos ? (_pos > _padding ? _pos - _padding : _pos) : 0;
+            const calculateCurrentIndex = (_pos, _size) => Math.floor(_pos / (_size || _pos));
+            const calculateTriggerIndex = (_currentIndex, _first, _last, _num, _isScrollDownOrRight) => {
+                return (_currentIndex <= this.d_numToleratedItems ? this.d_numToleratedItems : (_isScrollDownOrRight ? (_last - _num - this.d_numToleratedItems) : (_first + this.d_numToleratedItems - 1)))
+            };
+            const calculateFirst = (_currentIndex, _triggerIndex, _first, _last, _num, _isScrollDownOrRight) => {
+                if (_currentIndex <= this.d_numToleratedItems)
+                    return 0;
+                else
+                    return _isScrollDownOrRight ?
+                        (_currentIndex < _triggerIndex ? _first : _currentIndex - this.d_numToleratedItems) :
+                        (_currentIndex > _triggerIndex ? _first : _currentIndex - (2 * this.d_numToleratedItems));
+            };
+            const calculateLast = (_currentIndex, _first, _last, _num, _isCols) => {
+                let lastValue = _first + _num + (2 * this.d_numToleratedItems);
+
+                if (_currentIndex >= this.d_numToleratedItems) {
+                    lastValue += (this.d_numToleratedItems + 1);
+                }
+
+                return this.getLast(lastValue, _isCols);
+            };
+
+            const scrollTop = calculateScrollPos(target.scrollTop, contentPadding.top);
+            const scrollLeft = calculateScrollPos(target.scrollLeft, contentPadding.left);
+
+            let newFirst = 0;
+            let newLast = this.last;  
+            let isRangeChanged = false;
+
+            if (isBoth) {
+                const isScrollDown = this.lastScrollPos.top <= scrollTop;
+                const isScrollRight = this.lastScrollPos.left <= scrollLeft;
+                const currentIndex = { rows: calculateCurrentIndex(scrollTop, itemSize[0]), cols: calculateCurrentIndex(scrollLeft, itemSize[1]) };
+                const triggerIndex = {
+                    rows: calculateTriggerIndex(currentIndex.rows, this.first.rows, this.last.rows, this.numItemsInViewport.rows, isScrollDown),
+                    cols: calculateTriggerIndex(currentIndex.cols, this.first.cols, this.last.cols, this.numItemsInViewport.cols, isScrollRight)
+                };
+
+                newFirst = {
+                    rows: calculateFirst(currentIndex.rows, triggerIndex.rows, this.first.rows, this.last.rows, this.numItemsInViewport.rows, isScrollDown),
+                    cols: calculateFirst(currentIndex.cols, triggerIndex.cols, this.first.cols, this.last.cols, this.numItemsInViewport.cols, isScrollRight)
+                };
+                newLast = {
+                    rows: calculateLast(currentIndex.rows, newFirst.rows, this.last.rows, this.numItemsInViewport.rows),
+                    cols: calculateLast(currentIndex.cols, newFirst.cols, this.last.cols, this.numItemsInViewport.cols, true)
+                };
+                isRangeChanged = (newFirst.rows !== this.first.rows || newFirst.cols !== this.first.cols) || (newLast.rows !== this.last.rows || newLast.cols !== this.last.cols);
+
+                this.lastScrollPos = { top: scrollTop, left: scrollLeft };
+            }
+            else {
+                const scrollPos = isHorizontal ? scrollLeft : scrollTop;
+                const isScrollDownOrRight = this.lastScrollPos <= scrollPos;
+                const currentIndex = calculateCurrentIndex(scrollPos, itemSize);
+                const triggerIndex = calculateTriggerIndex(currentIndex, this.first, this.last, this.numItemsInViewport, isScrollDownOrRight);
+
+                newFirst = calculateFirst(currentIndex, triggerIndex, this.first, this.last, this.numItemsInViewport, isScrollDownOrRight);
+                newLast = calculateLast(currentIndex, newFirst, this.last, this.numItemsInViewport);
+                isRangeChanged = newFirst !== this.first || newLast !== this.last;
+
+                this.lastScrollPos = scrollPos;
+            }
+
+            return {
+                first: newFirst,
+                last: newLast,
+                isRangeChanged
+            }
+        },
+        onScrollChange(event) {
+            const { first, last, isRangeChanged } = this.onScrollPositionChange(event);
+
+            if (isRangeChanged) {
+                const newState = { first, last };
+            
+                this.setContentPosition(newState);
+            
+                if (this.lazy) {
+                    this.$emit('lazy-load', { first, last }); 
+                }
+                this.first = first;
+                this.last = last;
+            
+                this.$emit('scroll-index-change', { first, last });
+            }
+        },
+        onScroll(event) {
+            if (this.delay && !this.lazy) {
+                if (this.scrollTimeout) {
+                    clearTimeout(this.scrollTimeout);
+                }
+
+                if (!this.d_loading && this.showLoader) {
+                    const { isRangeChanged: changed } = this.onScrollPositionChange(event); 
+
+                    if (changed) {
+                        this.d_loading = true;
+                    }
+                }
+
+                this.scrollTimeout = setTimeout(() => {
+                    this.onScrollChange(event);
+
+                    if (this.d_loading && this.showLoader && !this.lazy) {
+                        this.d_loading = false;
+                    }
+                }, this.delay);
+            }
+            else {
+                this.onScrollChange(event);
+            }
+        },
+        getOptions(renderedIndex) {
+            let count = this.items.length;
+            let index = this.isBoth() ? this.first.rows + renderedIndex : this.first + renderedIndex;
+            return {
+                index,
+                count,
+                first: index === 0,
+                last: index === (count - 1),
+                even: index % 2 === 0,
+                odd: index % 2 !== 0
+            };
+        },
+        getLoaderOptions(index) {
+            let count = this.loaderArr.length;
+            return {
+                loading: this.d_loading,
+                first: index === 0,
+                last: index === (count - 1),
+                even: index % 2 === 0,
+                odd: index % 2 !== 0
+            }
+        },
+        isHorizontal() {
+            return this.orientation === 'horizontal';
+        },
+        isBoth() {
+            return this.orientation === 'both';
+        },
+        scrollTo(options) {
+            if (this.element) {
+                this.element.scrollTo(options);
+            }
+        },
+        scrollToIndex(index, behavior = 'auto') {
+            const isBoth = this.isBoth();
+            const isHorizontal = this.isHorizontal();
+            const itemSize = this.itemSize;
+            const contentPadding = this.getContentPadding();
+            const calculateFirst = (_index = 0) => (_index <= this.d_numToleratedItems ? 0 : _index);
+            const calculateCoord = (_first, _size, _padding) => (_first * _size) + _padding;
+            const scrollTo = (left = 0, top = 0) => this.scrollTo({ left, top, behavior });
+
+            if (isBoth) {
+                const newFirst = { rows: calculateFirst(index[0]), cols: calculateFirst(index[1]) };
+                if (newFirst.rows !== this.first.rows || newFirst.cols !== this.first.cols) 
+                    scrollTo(calculateCoord(newFirst.cols, itemSize[1], contentPadding.left),calculateCoord(newFirst.rows, itemSize[0], contentPadding.top));
+            }
+            else {
+                const newFirst = calculateFirst(index);
+
+                if (newFirst !== this.first) {
+                    isHorizontal ? scrollTo(calculateCoord(newFirst, itemSize, contentPadding.left), 0) : scrollTo(0, calculateCoord(newFirst, itemSize, contentPadding.top));
+                }
+
+                this.first = newFirst.index;
+            }
+        },
+        scrollInView(index, to, behavior = 'auto') {
+            if (to) { 
+                const isBoth = this.isBoth();
+                const isHorizontal = this.isHorizontal();
+                const { first, viewport } = this.getRenderedRange();
+                const itemSize = this.itemSize;
+                const scrollTo = (left = 0, top = 0) => this.scrollTo({ left, top, behavior });
+                const isToStart = to === 'to-start';
+                const isToEnd = to === 'to-end';
+
+                if (isToStart) {
+                    if (isBoth) {
+                        if (viewport.first.rows - first.rows > index[0]) {
+                            scrollTo(viewport.first.cols * itemSize[1], (viewport.first.rows - 1) * itemSize[0]);
+                        }
+                        else if (viewport.first.cols - first.cols > index[1]) {
+                            scrollTo((viewport.first.cols - 1) * itemSize[1], viewport.first.rows * itemSize[0]);
+                        }
+                    }
+                    else {
+                        if (viewport.first - first > index) {
+                            const pos = (viewport.first - 1) * itemSize;
+                            isHorizontal ? scrollTo(pos, 0) : scrollTo(0, pos);
+                        }
+                    }
+                }
+                else if (isToEnd) {
+                    if (isBoth) {
+                        if (viewport.last.rows - first.rows <= index[0] + 1) {
+                            scrollTo(viewport.first.cols * itemSize[1], (viewport.first.rows + 1) * itemSize[0]);
+                        }
+                        else if (viewport.last.cols - first.cols <= index[1] + 1) {
+                            scrollTo((viewport.first.cols + 1) * itemSize[1], viewport.first.rows * itemSize[0]);
+                        }
+                    }
+                    else {
+                        if (viewport.last - first <= index + 1) {
+                            const pos = (viewport.first + 1) * itemSize;
+                            isHorizontal ? scrollTo(pos, 0) : scrollTo(0, pos);
+                        }
+                    }
+                }
+            }
+            else {
+                this.scrollToIndex(index, behavior);
+            }
+        },
+        getRenderedRange() {
+            const isBoth = this.isBoth();
+            const isHorizontal = this.isHorizontal();
+            const itemSize = this.itemSize;
+            const calculateFirstInViewport = (_pos, _size) => Math.floor(_pos / (_size || _pos));
+
+            let firstInViewport = this.first;
+            let lastInViewport = 0;
+
+            if (this.element) {
+                const scrollTop = this.element.scrollTop;
+                const scrollLeft = this.element.scrollLeft;
+
+                if (isBoth) {
+                    firstInViewport = { rows: calculateFirstInViewport(scrollTop, itemSize[0]), cols: calculateFirstInViewport(scrollLeft, itemSize[1]) };
+                    lastInViewport = { rows: firstInViewport.rows + this.numItemsInViewport.rows, cols: firstInViewport.cols + this.numItemsInViewport.cols };
+                }
+                else {
+                    const scrollPos = isHorizontal ? scrollLeft : scrollTop;
+                    firstInViewport = calculateFirstInViewport(scrollPos, itemSize);
+                    lastInViewport = firstInViewport + this.numItemsInViewport;
+                }
+            }
+
+            return {
+                first: this.first,
+                last: this.last,
+                viewport: {
+                    first: firstInViewport,
+                    last: lastInViewport
+                }
+            };
+        },
+        elementRef(el) {
+            this.element = el;
+        },
+        contentRef(el) {
+            this.content = el;
+        },
+        spacerRef(el) {
+            this.spacer = el;
+        },
+    },
+    computed: {
+        containerClass() {
+            return ['p-virtualscroller', {
+                'p-both-scroll': this.isBoth(),
+                'p-horizontal-scroll': this.isHorizontal()
+            }, this.class];
+        },
+        loaderClass() {
+            return ['p-virtualscroller-loader', {
+                'p-component-overlay': !this.$slots.loader
+            }];
+        },
+        renderItems() {
+            const items = this.items;
+            if (items && !this.d_loading) {
+                const isBoth = this.isBoth();
+
+                if (isBoth) {
+                    return items.slice(this.first.rows, this.last.rows).map((item) => {
+                        const items = item.slice(this.first.cols, this.last.cols);
+                        return items;
+                    });
+                }
+                else {
+                    return items.slice(this.first, this.last).map((item) => {
+                        return item;
+                    });
+                }
+            }
+
+            return null;
+        }
+    }
+}
+</script>
+
+<style>
+.p-virtualscroller {
+    position: relative;
+    overflow: auto;
+    contain: strict;
+    transform: translateZ(0);
+    will-change: scroll-position;
+}
+
+.p-virtualscroller-content {
+    position: absolute;
+    top: 0;
+    left: 0;
+    contain: content;
+    min-height: 100%;
+    min-width: 100%;
+    will-change: transform;
+}
+
+.p-virtualscroller-spacer {
+    position: absolute;
+    top: 0;
+    left: 0;
+    height: 1px;
+    width: 1px;
+    transform-origin: 0 0;
+    pointer-events: none;
+}
+
+.p-virtualscroller .p-virtualscroller-loader {
+    position: sticky;
+    top: 0;
+    left: 0;
+    width: 100%;
+    height: 100%;
+}
+
+.p-virtualscroller-loader.p-component-overlay {
+    display: flex;
+    align-items: center;
+    justify-content: center;
+}
+</style>
\ No newline at end of file
diff --git a/src/components/virtualscroller/package.json b/src/components/virtualscroller/package.json
new file mode 100644
index 000000000..de1ab36fe
--- /dev/null
+++ b/src/components/virtualscroller/package.json
@@ -0,0 +1,9 @@
+{
+    "main": "./virtualscroller.cjs.js",
+    "module": "./virtualscroller.esm.js",
+    "unpkg": "./virtualscroller.min.js",
+    "types": "./VirtualScroller.d.ts",
+    "browser": {
+      "./sfc": "./VirtualScroller.vue"
+    }
+  }
\ No newline at end of file
diff --git a/src/main.js b/src/main.js
index 442ed9f6b..d54f26d2c 100644
--- a/src/main.js
+++ b/src/main.js
@@ -94,6 +94,7 @@ import Toolbar from './components/toolbar/Toolbar';
 import Tooltip from './components/tooltip/Tooltip';
 import TriStateCheckbox from './components/tristatecheckbox/TriStateCheckbox';
 import Galleria from './components/galleria/Galleria';
+import VirtualScroller from './components/virtualscroller/VirtualScroller';
 
 import AppInputStyleSwitch from './AppInputStyleSwitch';
 import AppDemoActions from './AppDemoActions';
@@ -210,6 +211,7 @@ app.component('TreeSelect', TreeSelect);
 app.component('TreeTable', TreeTable);
 app.component('TriStateCheckbox', TriStateCheckbox);
 app.component('Galleria', Galleria);
+app.component('VirtualScroller', VirtualScroller);
 
 app.component('AppDemoActions', AppDemoActions);
 app.component('AppInputStyleSwitch', AppInputStyleSwitch);
diff --git a/src/router/index.js b/src/router/index.js
index 8084b977f..d07b45819 100644
--- a/src/router/index.js
+++ b/src/router/index.js
@@ -831,6 +831,11 @@ const routes = [
         name: 'galleriaadvvanced',
         component: () => import('../views/galleria/GalleriaAdvancedDemo.vue')
     },
+    {
+        path: '/virtualscroller',
+        name: 'virtualscroller',
+        component: () => import('../views/virtualscroller/VirtualScrollerDemo.vue')
+    },
     {
         path: '/vuelidate',
         name: 'vuelidateform',
diff --git a/src/views/liveeditor/LiveEditor.vue b/src/views/liveeditor/LiveEditor.vue
index 276bc7298..ba0e903c7 100644
--- a/src/views/liveeditor/LiveEditor.vue
+++ b/src/views/liveeditor/LiveEditor.vue
@@ -490,6 +490,7 @@ import Tree from 'primevue/tree';
 import TreeSelect from 'primevue/treeselect';
 import TreeTable from 'primevue/treetable';
 import TriStateCheckbox from 'primevue/tristatecheckbox';
+import VirtualScroller from 'primevue/virtualscroller';
 ${extImport}
 
 const app = createApp(${name});
@@ -586,6 +587,7 @@ app.component('Tree', Tree);
 app.component('TreeSelect', TreeSelect);
 app.component('TreeTable', TreeTable);
 app.component('TriStateCheckbox', TriStateCheckbox);
+app.component('VirtualScroller', VirtualScroller);
 ${extElement}
 
 app.mount("#app");
diff --git a/src/views/virtualscroller/VirtualScrollerDemo.vue b/src/views/virtualscroller/VirtualScrollerDemo.vue
new file mode 100644
index 000000000..51d5b3d02
--- /dev/null
+++ b/src/views/virtualscroller/VirtualScrollerDemo.vue
@@ -0,0 +1,243 @@
+<template>
+    <div>
+        <div class="content-section introduction">
+            <div class="feature-intro">
+                <h1>VirtualScroller</h1>
+                <p>VirtualScroller is a performant approach to handle huge data efficiently.</p>
+            </div>
+            <AppDemoActions />
+        </div>
+
+        <div class="content-section implementation virtualscroller-demo">
+            <div class="card">
+                <h5 class="p-mb-0">Basic</h5>
+                <div class="p-d-flex p-ai-center p-flex-wrap">
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <h6>Vertical</h6>
+                        <VirtualScroller :items="basicItems" :itemSize="50">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px">{{ item }}</div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <h6>Horizontal</h6>
+                        <VirtualScroller :items="basicItems" :itemSize="50" orientation="horizontal">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="width: 50px">{{ item }}</div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <h6>Both</h6>
+                        <VirtualScroller :items="multiItems" :itemSize="[50, 100]" orientation="both">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px" >
+                                    <template v-for="(el, index) of item" :key="index">
+                                        <div style="width: 100px">{{ el }}</div>
+                                    </template>
+                                </div>
+                            </template>
+                        </VirtualScroller>
+                    </div> 
+                </div>
+            </div>
+
+            <div class="card">
+                <h5 class="p-mb-0">Scroll Delay</h5>
+                <div class="p-d-flex p-ai-center p-flex-wrap">
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <h6>0ms Delay</h6>
+                        <VirtualScroller :items="basicItems" :itemSize="50">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px">{{ item }}</div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <h6>150ms Delay</h6>
+                        <VirtualScroller :items="basicItems" :itemSize="50" :delay="150">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px">{{ item }}</div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <h6>250ms Delay</h6>
+                        <VirtualScroller :items="basicItems" :itemSize="50" :delay="250">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px">{{ item }}</div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+                </div>
+            </div>
+
+            <div class="card">
+                <h5 class="p-mb-0">Loading</h5>
+                <div class="p-d-flex p-ai-center p-flex-wrap">
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <h6>Basic</h6>
+                        <VirtualScroller :items="basicItems" :itemSize="50" showLoader :delay="250">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px">{{ item }}</div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <h6>Templating</h6>
+                        <VirtualScroller class="custom-loading" :items="basicItems" :itemSize="50" showLoader :delay="250">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px">{{ item }}</div>
+                            </template>
+                            <template v-slot:loader="{ options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px" >
+                                    <Skeleton :width="options.even ? '60%' : '50%'" height="1.3rem" />
+                                </div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+                </div>
+            </div>
+
+            <div class="card">
+                <h5 class="p-mb-0">Lazy</h5>
+                <div class="p-d-flex p-ai-center p-flex-wrap">
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <VirtualScroller :items="lazyItems" :itemSize="50" showLoader :delay="250" :loading="lazyLoading" :lazy=true @lazy-load="onLazyLoad">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px">{{ item }}</div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+                </div>
+            </div>
+
+            <div class="card">
+                <h5 class="p-mb-0">Template</h5>
+                <div class="p-d-flex p-ai-center p-flex-wrap">
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <VirtualScroller class="custom-loading" :items="basicItems" :itemSize="25 * 7" showLoader :delay="250">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['custom-scroll-item scroll-item', {'odd': options.odd}]">
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px">{{`Item: ${item}`}}</div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px">{{`Index: ${options.index}`}}</div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px">{{`Count: ${options.count}`}}</div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px">{{`First: ${options.first}`}}</div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px">{{`Last: ${options.last}`}}</div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px">{{`Even: ${options.even}`}}</div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px">{{`Odd: ${options.odd}`}}</div>
+                                </div>
+                            </template>
+                            <template v-slot:loader="{ options }">
+                                <div :class="['custom-scroll-item scroll-item', {'odd': options.odd}]">
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px"><Skeleton width="60%" height="1.2rem" /></div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px"><Skeleton width="50%" height="1.2rem" /></div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px"><Skeleton width="60%" height="1.2rem" /></div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px"><Skeleton width="50%" height="1.2rem" /></div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px"><Skeleton width="60%" height="1.2rem" /></div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px"><Skeleton width="50%" height="1.2rem" /></div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px"><Skeleton width="60%" height="1.2rem" /></div>
+                                </div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+                </div>
+            </div>
+        </div>
+
+        <VirtualScrollerDoc />
+    </div>
+</template>
+
+<script>
+import VirtualScrollerDoc from './VirtualScrollerDoc.vue';
+
+export default {
+    data() {
+        return {
+            basicItems: null,
+            multiItems: null,
+            lazyItems: null,
+            lazyLoading: false,
+            loadLazyTimeout: null,
+        }
+    },
+    mounted() {
+        this.basicItems = Array.from({ length: 100000 }).map((_, i) => `Item #${i}`);
+        this.multiItems = Array.from({ length: 1000 }).map((_, i) => Array.from({ length: 1000 }).map((_j, j) => `Item #${i}_${j}`));
+        this.lazyItems = Array.from({ length: 100000 });
+    },
+    methods: {
+        onLazyLoad(event) {
+            this.lazyLoading = true;
+
+            if (this.loadLazyTimeout) {
+                clearTimeout(this.loadLazyTimeout);
+            }
+            
+            //imitate delay of a backend call
+            this.loadLazyTimeout = setTimeout(() => {
+                const { first, last } = event;
+                const lazyItems = [...this.lazyItems];
+            
+                for (let i = first; i < last; i++) {
+                    lazyItems[i] = `Item #${i}`;
+                }
+
+                this.lazyItems = lazyItems;
+                this.lazyLoading = false;
+
+            }, Math.random() * 1000 + 250);
+        }
+    },
+    components: {
+        VirtualScrollerDoc
+    }
+}
+</script>
+
+<style lang="scss" scoped>
+.virtualscroller-demo {
+	::v-deep(.p-virtualscroller) {
+		height: 200px;
+		width: 200px;
+		border: 1px solid var(--surface-d);
+
+        .scroll-item {
+            background-color: var(--surface-a);
+            display: flex;
+            align-items: center;
+        }
+
+        .custom-scroll-item {
+            flex-direction: column;
+            align-items: stretch;
+        }
+
+        .odd {
+            background-color: var(--surface-b);
+        }
+	}
+
+    ::v-deep(.p-horizontal-scroll) {
+        .p-virtualscroller-content {
+            display: flex;
+            flex-direction: row;
+        }
+        
+        .scroll-item {
+            writing-mode: vertical-lr;
+        }
+    }
+
+    ::v-deep(.custom-loading > .p-virtualscroller-loader) {
+        display: block;
+    }
+}
+</style>
\ No newline at end of file
diff --git a/src/views/virtualscroller/VirtualScrollerDoc.vue b/src/views/virtualscroller/VirtualScrollerDoc.vue
new file mode 100644
index 000000000..7924ad70f
--- /dev/null
+++ b/src/views/virtualscroller/VirtualScrollerDoc.vue
@@ -0,0 +1,824 @@
+<template>
+    <AppDoc name="VirtualScrollerDemo" :sources="sources" github="virtualscroller/VirtualScrollerDemo.vue">
+        <h5>Imports</h5>
+<pre v-code.script><code>
+import VirtualScroller from 'primevue/virtualscroller';   
+
+</code></pre>
+
+        <h5>Getting Started</h5>
+        <p>VirtualScroller is used to display huge data. It periodically adds special elements defined according to the scroll's position to the DOM.
+            The <i>item</i> and <i>itemSize</i> properties and <i>item</i> template are required on component. In addition, an initial array is required based on the total number of items to display.<br />
+            VirtualScroller automatically calculates how many items will be displayed in the view according to <i>itemSize</i> using a specified scroll height. Its scroll height can be adjusted with <i>scrollHeight</i>
+            property or height property of CSS.</p>
+    
+<pre v-code><code><template v-pre>
+&lt;VirtualScroller :items="basicItems" :itemSize="50"&gt;
+    &lt;template v-slot:item="{ item, options }"&gt;
+        &lt;div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px"&gt;{{ item }}&lt;/div&gt;
+    &lt;/template&gt;
+&lt;/VirtualScroller&gt;
+</template>
+</code></pre>
+
+<pre v-code.script><code>
+export default {
+    data() {
+        return {
+            basicItems: null
+        }
+    },
+    mounted() {
+        this.basicItems = Array.from({ length: 100000 }).map((_, i) => `Item #${i}`);
+    }
+}
+
+</code></pre>
+
+        <h5>Loader</h5>
+        <p>VirtualScroller has a special loader. It can be activated with the <i>showLoader</i> property.
+            In addition, <i>loader</i> template can be used to add custom loaders to item elements.</p>
+
+<pre v-code><code><template v-pre>
+&lt;VirtualScroller :items="basicItems" :itemSize="50" showLoader :delay="250"&gt;
+    &lt;template v-slot:item="{ item, options }"&gt;
+        &lt;div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px"&gt;{{ item }}&lt;/div&gt;
+    &lt;/template&gt;
+    &lt;template v-slot:loader="{ options }"&gt;
+        &lt;div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px" &gt;
+            &lt;Skeleton :width="options.even ? '60%' : '50%'" height="1.3rem" /&gt;
+        &lt;/div&gt;
+    &lt;/template&gt;
+&lt;/VirtualScroller&gt;
+</template>
+</code></pre>
+
+        <h5>Lazy</h5>
+        <p>Lazy mode is handy to deal with large datasets, instead of loading the entire data, small chunks of data is loaded by invoking <i>lazy-load</i> event.</p>
+
+<pre v-code><code><template v-pre>
+&lt;VirtualScroller :items="lazyItems" :itemSize="50" showLoader :delay="250" :loading="lazyLoading" :lazy=true @lazy-load="onLazyLoad"&gt;
+    &lt;template v-slot:item="{ item, options }"&gt;
+        &lt;div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px"&gt;{{ item }}&lt;/div&gt;
+    &lt;/template&gt;
+&lt;/VirtualScroller&gt;
+</template>
+</code></pre>
+
+<pre v-code.script><code>
+export default {
+    data() {
+        return {
+            lazyItems: null,
+            lazyLoading: false,
+            loadLazyTimeout: null,
+        }
+    },
+    mounted() {
+        this.lazyItems = Array.from({ length: 100000 });
+    },
+    methods: {
+        onLazyLoad(event) {
+            this.lazyLoading = true;
+
+            if (this.loadLazyTimeout) {
+                clearTimeout(this.loadLazyTimeout);
+            }
+            
+            //imitate delay of a backend call
+            this.loadLazyTimeout = setTimeout(() => {
+                const { first, last } = event;
+                const lazyItems = [...this.lazyItems];
+            
+                for (let i = first; i &lt; last; i++) {
+                    lazyItems[i] = `Item #${i}`;
+                }
+
+                this.lazyItems = lazyItems;
+                this.lazyLoading = false;
+
+            }, Math.random() * 1000 + 250);
+        }
+    }
+}
+
+</code></pre>
+
+        <h5>Properties</h5>
+        <div class="doc-tablewrapper">
+            <table class="doc-table">
+                <thead>
+                    <tr>
+                        <th>Name</th>
+                        <th>Type</th>
+                        <th>Default</th>
+                        <th>Description</th>
+                    </tr>
+                </thead>
+                <tbody>
+                    <tr>
+                        <td>items</td>
+                        <td>array</td>
+                        <td>null</td>
+                        <td>An array of objects to display.</td>
+                    </tr>
+                    <tr>
+                        <td>itemSize</td>
+                        <td>number / [number, number]</td>
+                        <td>null</td>
+                        <td>The height/width of item according to orientation.</td>
+                    </tr>
+                    <tr>
+                        <td>scrollHeight</td>
+                        <td>string</td>
+                        <td>null</td>
+                        <td>Height of the scroll viewport.</td>
+                    </tr>
+                    <tr>
+                        <td>scrollWidth</td>
+                        <td>string</td>
+                        <td>null</td>
+                        <td>Width of the scroll viewport.</td>
+                    </tr>
+                    <tr>
+                        <td>orientation</td>
+                        <td>string</td>
+                        <td>'vertical'</td>
+                        <td>The orientation of scrollbar, valid values are 'vertical', 'horizontal' and 'both'.</td>
+                    </tr>
+                    <tr>
+                        <td>numToleratedItems</td>
+                        <td>number</td>
+                        <td>null</td>
+                        <td>Determines how many additional elements to add to the DOM outside of the view. <br />
+                            According to the scrolls made up and down, extra items are added in a certain algorithm in the form of multiples of this number. <br />
+                            Default value is half the number of items shown in the view.</td>
+                    </tr>
+                    <tr>
+                        <td>delay</td>
+                        <td>number</td>
+                        <td>0</td>
+                        <td>Delay in scroll before new data is loaded.</td>
+                    </tr>
+                    <tr>
+                        <td>lazy</td>
+                        <td>boolean</td>
+                        <td>false</td>
+                        <td>Defines if data is loaded and interacted with in lazy manner.</td>
+                    </tr>
+                    <tr>
+                        <td>showLoader</td>
+                        <td>boolean</td>
+                        <td>false</td>
+                        <td>Whether to show loader.</td>
+                    </tr>
+                    <tr>
+                        <td>style</td>
+                        <td>any</td>
+                        <td>null</td>
+                        <td>Inline style of the component.</td>
+                    </tr>
+                    <tr>
+                        <td>class</td>
+                        <td>string</td>
+                        <td>null</td>
+                        <td>Style class of the component.</td>
+                    </tr>
+                </tbody>
+            </table>
+        </div>
+
+        <h5>Events</h5>
+        <div class="doc-tablewrapper">
+            <table class="doc-table">
+                <thead>
+                    <tr>
+                        <th>Name</th>
+                        <th>Parameters</th>
+                        <th>Description</th>
+                    </tr>
+                </thead>
+                <tbody>
+                    <tr>
+                        <td>scroll</td>
+                        <td>event: Browser event</td>
+                        <td>Callback to invoke when scroll position changes.</td>
+                    </tr>
+                    <tr>
+                        <td>scroll-index-change</td>
+                        <td>event.first: First index of the new data range to be loaded.<br/>
+                            event.last: Last index of the new data range to be loaded.
+                        </td>
+                        <td>Callback to invoke when scroll position and item's range in view changes.</td>
+                    </tr>
+                    <tr>
+                        <td>lazy-load</td>
+                        <td>event.first: First index of the new data range to be loaded.<br/>
+                            event.last: Last index of the new data range to be loaded.
+                        </td>
+                        <td>Callback to invoke in lazy mode to load new data.</td>
+                    </tr>
+                </tbody>
+            </table>
+        </div>
+
+        <h5>Methods</h5>
+        <div class="doc-tablewrapper">
+            <table class="doc-table">
+                <thead>
+                    <tr>
+                        <th>Name</th>
+                        <th>Parameters</th>
+                        <th>Description</th>
+                    </tr>
+                </thead>
+                <tbody>
+                    <tr>
+                        <td>scrollTo</td>
+                        <td>
+                            left: Left position of scroll. <br />
+                            top: Top position of scroll <br />
+                            behavior: Behavior of scroll, valid values are 'auto' and 'smooth'
+                        </td>
+                        <td>Scroll to move to a specific position.</td>
+                    </tr>
+                    <tr>
+                        <td>scrollToIndex</td>
+                        <td>
+                            index: Index of item according to orientation mode. <br />
+                            behavior: Behavior of scroll, valid values are 'auto' and 'smooth'
+                        </td>
+                        <td>Scroll to move to a specific item.</td>
+                    </tr>
+                    <tr>
+                        <td>scrollInView</td>
+                        <td>
+                            index: Index of item according to orientation mode. <br />
+                            to: Defines the location of the item in view, valid values are 'to-start' and 'to-end'. <br />
+                            behavior: Behavior of scroll, valid values are 'auto' and 'smooth'
+                        </td>
+                        <td>It is used to move the specified index into the view. It is a method that will usually be needed when keyboard support is added to the virtualScroller component.</td>
+                    </tr>
+                    <tr>
+                        <td>getRenderedRange</td>
+                        <td>-</td>
+                        <td>Returns the range of items added to the DOM.</td>
+                    </tr>
+                </tbody>
+            </table>
+        </div>
+
+        <h5>Slots</h5>
+        <div class="doc-tablewrapper">
+            <table class="doc-table">
+                <thead>
+                    <tr>
+                        <th>Name</th>
+                        <th>Parameters</th>
+                    </tr>
+                </thead>
+                <tbody>
+                    <tr>
+                        <td>item</td>
+                        <td>item: Item instance<br />
+                            options: Options of the item instance</td>
+                    </tr>
+                    <tr>
+                        <td>loader</td>
+                        <td>options: Options of the loader items</td>
+                    </tr>
+                </tbody>
+            </table>
+        </div>
+
+        <h5>Styling</h5>
+        <p>Following is the list of structural style classes, for theming classes visit <router-link to="/theming">theming</router-link> page.</p>
+        <div class="doc-tablewrapper">
+            <table class="doc-table">
+                <thead>
+                    <tr>
+                        <th>Name</th>
+                        <th>Element</th>
+                    </tr>
+                </thead>
+                <tbody>
+                    <tr>
+                        <td>p-virtualscroller</td>
+                        <td>Container element.</td>
+                    </tr>
+                    <tr>
+                        <td>p-virtualscroller-content</td>
+                        <td>Content element.</td>
+                    </tr>
+                    <tr>
+                        <td>p-virtualscroller-loader</td>
+                        <td>Loader element.</td>
+                    </tr>
+                </tbody>
+            </table>
+        </div>
+
+        <h5>Dependencies</h5>
+        <p>None.</p>
+
+    </AppDoc>
+</template>
+
+<script>
+export default {
+    data() {
+        return { 
+            sources: {
+                'options-api': {
+                    tabName: 'Options API Source',
+                    content: `
+<template>
+    <div>
+        <div class="content-section introduction">
+            <div class="feature-intro">
+                <h1>VirtualScroller</h1>
+                <p>VirtualScroller is a performant approach to handle huge data efficiently.</p>
+            </div>
+            <AppDemoActions />
+        </div>
+
+        <div class="content-section implementation virtualscroller-demo">
+            <div class="card">
+                <h5 class="p-mb-0">Basic</h5>
+                <div class="p-d-flex p-ai-center p-flex-wrap">
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <h6>Vertical</h6>
+                        <VirtualScroller :items="basicItems" :itemSize="50">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px">{{ item }}</div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <h6>Horizontal</h6>
+                        <VirtualScroller :items="basicItems" :itemSize="50" orientation="horizontal">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="width: 50px">{{ item }}</div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <h6>Both</h6>
+                        <VirtualScroller :items="multiItems" :itemSize="[50, 100]" orientation="both">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px" >
+                                    <template v-for="(el, index) of item" :key="index">
+                                        <div style="width: 100px">{{ el }}</div>
+                                    </template>
+                                </div>
+                            </template>
+                        </VirtualScroller>
+                    </div> 
+                </div>
+            </div>
+
+            <div class="card">
+                <h5 class="p-mb-0">Scroll Delay</h5>
+                <div class="p-d-flex p-ai-center p-flex-wrap">
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <h6>0ms Delay</h6>
+                        <VirtualScroller :items="basicItems" :itemSize="50">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px">{{ item }}</div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <h6>150ms Delay</h6>
+                        <VirtualScroller :items="basicItems" :itemSize="50" :delay="150">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px">{{ item }}</div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <h6>250ms Delay</h6>
+                        <VirtualScroller :items="basicItems" :itemSize="50" :delay="250">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px">{{ item }}</div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+                </div>
+            </div>
+
+            <div class="card">
+                <h5 class="p-mb-0">Loading</h5>
+                <div class="p-d-flex p-ai-center p-flex-wrap">
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <h6>Basic</h6>
+                        <VirtualScroller :items="basicItems" :itemSize="50" showLoader :delay="250">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px">{{ item }}</div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <h6>Templating</h6>
+                        <VirtualScroller class="custom-loading" :items="basicItems" :itemSize="50" showLoader :delay="250">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px">{{ item }}</div>
+                            </template>
+                            <template v-slot:loader="{ options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px" >
+                                    <Skeleton :width="options.even ? '60%' : '50%'" height="1.3rem" />
+                                </div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+                </div>
+            </div>
+
+            <div class="card">
+                <h5 class="p-mb-0">Lazy</h5>
+                <div class="p-d-flex p-ai-center p-flex-wrap">
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <VirtualScroller :items="lazyItems" :itemSize="50" showLoader :delay="250" :loading="lazyLoading" :lazy=true @lazy-load="onLazyLoad">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px">{{ item }}</div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+                </div>
+            </div>
+
+            <div class="card">
+                <h5 class="p-mb-0">Template</h5>
+                <div class="p-d-flex p-ai-center p-flex-wrap">
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <VirtualScroller class="custom-loading" :items="basicItems" :itemSize="25 * 7" showLoader :delay="250">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['custom-scroll-item scroll-item', {'odd': options.odd}]">
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px">{{\`Item: \${item}\`}}</div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px">{{\`Index: \${options.index}\`}}</div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px">{{\`Count: \${options.count}\`}}</div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px">{{\`First: \${options.first}\`}}</div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px">{{\`Last: \${options.last}\`}}</div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px">{{\`Even: \${options.even}\`}}</div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px">{{\`Odd: \${options.odd}\`}}</div>
+                                </div>
+                            </template>
+                            <template v-slot:loader="{ options }">
+                                <div :class="['custom-scroll-item scroll-item', {'odd': options.odd}]">
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px"><Skeleton width="60%" height="1.2rem" /></div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px"><Skeleton width="50%" height="1.2rem" /></div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px"><Skeleton width="60%" height="1.2rem" /></div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px"><Skeleton width="50%" height="1.2rem" /></div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px"><Skeleton width="60%" height="1.2rem" /></div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px"><Skeleton width="50%" height="1.2rem" /></div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px"><Skeleton width="60%" height="1.2rem" /></div>
+                                </div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+                </div>
+            </div>
+        </div>
+    </div>
+</template>
+
+<script>
+export default {
+    data() {
+        return {
+            basicItems: null,
+            multiItems: null,
+            lazyItems: null,
+            lazyLoading: false,
+            loadLazyTimeout: null,
+        }
+    },
+    mounted() {
+        this.basicItems = Array.from({ length: 100000 }).map((_, i) => \`Item #\${i}\`);
+        this.multiItems = Array.from({ length: 1000 }).map((_, i) => Array.from({ length: 1000 }).map((_j, j) => \`Item #\${i}_\${j}\`));
+        this.lazyItems = Array.from({ length: 100000 });
+    },
+    methods: {
+        onLazyLoad(event) {
+            this.lazyLoading = true;
+
+            if (this.loadLazyTimeout) {
+                clearTimeout(this.loadLazyTimeout);
+            }
+            
+            //imitate delay of a backend call
+            this.loadLazyTimeout = setTimeout(() => {
+                const { first, last } = event;
+                const lazyItems = [...this.lazyItems];
+            
+                for (let i = first; i < last; i++) {
+                    lazyItems[i] = \`Item #\${i}\`;
+                }
+
+                this.lazyItems = lazyItems;
+                this.lazyLoading = false;
+
+            }, Math.random() * 1000 + 250);
+        }
+    }
+}
+<\\/script>
+
+<style lang="scss" scoped>
+.virtualscroller-demo {
+	::v-deep(.p-virtualscroller) {
+		height: 200px;
+		width: 200px;
+		border: 1px solid var(--surface-d);
+
+        .scroll-item {
+            background-color: var(--surface-a);
+            display: flex;
+            align-items: center;
+        }
+
+        .custom-scroll-item {
+            flex-direction: column;
+            align-items: stretch;
+        }
+
+        .odd {
+            background-color: var(--surface-b);
+        }
+	}
+
+    ::v-deep(.p-horizontal-scroll) {
+        .p-virtualscroller-content {
+            display: flex;
+            flex-direction: row;
+        }
+        
+        .scroll-item {
+            writing-mode: vertical-lr;
+        }
+    }
+
+    ::v-deep(.custom-loading > .p-virtualscroller-loader) {
+        display: block;
+    }
+}
+</style>
+
+`
+                },
+                'composition-api': {
+                    tabName: 'Composition API Source', 
+                    content: `
+<template>
+    <div>
+        <div class="content-section introduction">
+            <div class="feature-intro">
+                <h1>VirtualScroller</h1>
+                <p>VirtualScroller is a performant approach to handle huge data efficiently.</p>
+            </div>
+            <AppDemoActions />
+        </div>
+
+        <div class="content-section implementation virtualscroller-demo">
+            <div class="card">
+                <h5 class="p-mb-0">Basic</h5>
+                <div class="p-d-flex p-ai-center p-flex-wrap">
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <h6>Vertical</h6>
+                        <VirtualScroller :items="basicItems" :itemSize="50">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px">{{ item }}</div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <h6>Horizontal</h6>
+                        <VirtualScroller :items="basicItems" :itemSize="50" orientation="horizontal">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="width: 50px">{{ item }}</div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <h6>Both</h6>
+                        <VirtualScroller :items="multiItems" :itemSize="[50, 100]" orientation="both">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px" >
+                                    <template v-for="(el, index) of item" :key="index">
+                                        <div style="width: 100px">{{ el }}</div>
+                                    </template>
+                                </div>
+                            </template>
+                        </VirtualScroller>
+                    </div> 
+                </div>
+            </div>
+
+            <div class="card">
+                <h5 class="p-mb-0">Scroll Delay</h5>
+                <div class="p-d-flex p-ai-center p-flex-wrap">
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <h6>0ms Delay</h6>
+                        <VirtualScroller :items="basicItems" :itemSize="50">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px">{{ item }}</div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <h6>150ms Delay</h6>
+                        <VirtualScroller :items="basicItems" :itemSize="50" :delay="150">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px">{{ item }}</div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <h6>250ms Delay</h6>
+                        <VirtualScroller :items="basicItems" :itemSize="50" :delay="250">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px">{{ item }}</div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+                </div>
+            </div>
+
+            <div class="card">
+                <h5 class="p-mb-0">Loading</h5>
+                <div class="p-d-flex p-ai-center p-flex-wrap">
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <h6>Basic</h6>
+                        <VirtualScroller :items="basicItems" :itemSize="50" showLoader :delay="250">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px">{{ item }}</div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <h6>Templating</h6>
+                        <VirtualScroller class="custom-loading" :items="basicItems" :itemSize="50" showLoader :delay="250">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px">{{ item }}</div>
+                            </template>
+                            <template v-slot:loader="{ options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px" >
+                                    <Skeleton :width="options.even ? '60%' : '50%'" height="1.3rem" />
+                                </div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+                </div>
+            </div>
+
+            <div class="card">
+                <h5 class="p-mb-0">Lazy</h5>
+                <div class="p-d-flex p-ai-center p-flex-wrap">
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <VirtualScroller :items="lazyItems" :itemSize="50" showLoader :delay="250" :loading="lazyLoading" :lazy=true @lazy-load="onLazyLoad">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['scroll-item p-p-2', {'odd': options.odd}]" style="height: 50px">{{ item }}</div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+                </div>
+            </div>
+
+            <div class="card">
+                <h5 class="p-mb-0">Template</h5>
+                <div class="p-d-flex p-ai-center p-flex-wrap">
+                    <div class="p-d-flex p-dir-col p-mr-3 p-mt-3">
+                        <VirtualScroller class="custom-loading" :items="basicItems" :itemSize="25 * 7" showLoader :delay="250">
+                            <template v-slot:item="{ item, options }">
+                                <div :class="['custom-scroll-item scroll-item', {'odd': options.odd}]">
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px">{{\`Item: \${item}\`}}</div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px">{{\`Index: \${options.index}\`}}</div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px">{{\`Count: \${options.count}\`}}</div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px">{{\`First: \${options.first}\`}}</div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px">{{\`Last: \${options.last}\`}}</div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px">{{\`Even: \${options.even}\`}}</div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px">{{\`Odd: \${options.odd}\`}}</div>
+                                </div>
+                            </template>
+                            <template v-slot:loader="{ options }">
+                                <div :class="['custom-scroll-item scroll-item', {'odd': options.odd}]">
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px"><Skeleton width="60%" height="1.2rem" /></div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px"><Skeleton width="50%" height="1.2rem" /></div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px"><Skeleton width="60%" height="1.2rem" /></div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px"><Skeleton width="50%" height="1.2rem" /></div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px"><Skeleton width="60%" height="1.2rem" /></div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px"><Skeleton width="50%" height="1.2rem" /></div>
+                                    <div class="p-d-flex p-ai-center p-px-2" style="height: 25px"><Skeleton width="60%" height="1.2rem" /></div>
+                                </div>
+                            </template>
+                        </VirtualScroller>
+                    </div>
+                </div>
+            </div>
+        </div>
+    </div>
+</template>
+
+<script>
+import { ref, onMounted } from 'vue';
+
+export default {
+    setup() {
+        onMounted(() => {
+            basicItems.value = Array.from({ length: 100000 }).map((_, i) => \`Item #\${i}\`);
+            multiItems.value = Array.from({ length: 1000 }).map((_, i) => Array.from({ length: 1000 }).map((_j, j) => \`Item #\${i}_\${j}\`));
+            lazyItems.value = Array.from({ length: 100000 });
+        })
+
+        const basicItems = ref(null);
+        const multiItems = ref(null);
+        const lazyItems = ref(null);
+        const lazyLoading = ref(false);
+        const loadLazyTimeout = ref(null);
+
+        const onLazyLoad = (event) => {
+            lazyLoading.value = true;
+
+            if (loadLazyTimeout.value) {
+                clearTimeout(loadLazyTimeout.value);
+            }
+            
+            //imitate delay of a backend call
+            loadLazyTimeout.value = setTimeout(() => {
+                const { first, last } = event;
+                const lazyItems = [...lazyItems.value];
+            
+                for (let i = first; i < last; i++) {
+                    lazyItems[i] = \`Item #\${i}\`;
+                }
+
+                lazyItems.value = lazyItems;
+                lazyLoading.value = false;
+
+            }, Math.random() * 1000 + 250);
+        }
+
+        return { basicItems, multiItems, lazyItems, lazyLoading, onLazyLoad }
+    },
+    methods: {
+        
+    }
+}
+<\\/script>
+
+<style lang="scss" scoped>
+.virtualscroller-demo {
+	::v-deep(.p-virtualscroller) {
+		height: 200px;
+		width: 200px;
+		border: 1px solid var(--surface-d);
+
+        .scroll-item {
+            background-color: var(--surface-a);
+            display: flex;
+            align-items: center;
+        }
+
+        .custom-scroll-item {
+            flex-direction: column;
+            align-items: stretch;
+        }
+
+        .odd {
+            background-color: var(--surface-b);
+        }
+	}
+
+    ::v-deep(.p-horizontal-scroll) {
+        .p-virtualscroller-content {
+            display: flex;
+            flex-direction: row;
+        }
+        
+        .scroll-item {
+            writing-mode: vertical-lr;
+        }
+    }
+
+    ::v-deep(.custom-loading > .p-virtualscroller-loader) {
+        display: block;
+    }
+}
+</style>
+`
+                }
+            }
+        }
+    }
+}
+</script>
\ No newline at end of file