primevue-mirror/doc/multiselect/InvalidDoc.vue

<template>
    <DocSectionText v-bind="$attrs">
        <p>Invalid state is displayed using the <i>invalid</i> prop to indicate a failed validation. You can use this style when integrating with form validation libraries.</p>
    </DocSectionText>
    <div class="card flex justify-center">
        <MultiSelect v-model="selectedCities" :options="cities" optionLabel="name" filter placeholder="Select Cities" :maxSelectedLabels="3" :invalid="selectedCities?.length === 0" class="w-full md:w-80" />
    </div>
    <DocSectionCode :code="code" />
</template>

<script>
export default {
    data() {
        return {
            selectedCities: [],
            cities: [
                { name: 'New York', code: 'NY' },
                { name: 'Rome', code: 'RM' },
                { name: 'London', code: 'LDN' },
                { name: 'Istanbul', code: 'IST' },
                { name: 'Paris', code: 'PRS' }
            ],
            code: {
                basic: `
<MultiSelect v-model="selectedCities" :options="cities" optionLabel="name" filter placeholder="Select Cities"
    :maxSelectedLabels="3" :invalid="selectedCities === null"  class="w-full md:w-80" />
`,
                options: `
<template>
    <div class="card flex justify-center">
        <MultiSelect v-model="selectedCities" :options="cities" optionLabel="name" filter placeholder="Select Cities"
            :maxSelectedLabels="3" :invalid="selectedCities === null"  class="w-full md:w-80" />
    </div>
</template>

<script>
export default {
    data() {
        return {
            selectedCities: [],
            cities: [
                { name: 'New York', code: 'NY' },
                { name: 'Rome', code: 'RM' },
                { name: 'London', code: 'LDN' },
                { name: 'Istanbul', code: 'IST' },
                { name: 'Paris', code: 'PRS' }
            ]
        };
    }
};
<\/script>
`,
                composition: `
<template>
    <div class="card flex justify-center">
        <MultiSelect v-model="selectedCities" :options="cities" optionLabel="name" filter placeholder="Select Cities"
            :maxSelectedLabels="3" :invalid="selectedCities === null"  class="w-full md:w-80" />
    </div>
</template>

<script setup>
import { ref } from "vue";

const selectedCities = ref([]);
const cities = ref([
    { name: 'New York', code: 'NY' },
    { name: 'Rome', code: 'RM' },
    { name: 'London', code: 'LDN' },
    { name: 'Istanbul', code: 'IST' },
    { name: 'Paris', code: 'PRS' }
]);
<\/script>
`
            }
        };
    }
};
</script>