Added style class definitions to *Style.d.ts

components/lib/tree/style/TreeStyle.d.ts

@@ -1,3 +1,30 @@
+/**
+ *
+ * Tree is used to display hierarchical data.
+ *
+ * [Live Demo](https://www.primevue.org/tree/)
+ *
+ * @module treestyle
+ *
+ */
 import { BaseStyle } from '../../base/style';
 
+export enum TreeClasses {
+    root = 'p-tree',
+    mask = 'p-tree-mask',
+    loadingIcon = 'p-tree-loading-icon',
+    pcFilterInput = 'p-tree-filter-input',
+    wrapper = 'p-tree-root',
+    rootChildren = 'p-tree-root-children',
+    node = 'p-tree-node',
+    nodeContent = 'p-tree-node-content',
+    nodeToggleButton = 'p-tree-node-toggle-button',
+    nodeToggleIcon = 'p-tree-node-toggle-icon',
+    nodeTogglerIcon = 'p-tree-node-toggler-icon',
+    nodeCheckbox = 'p-tree-node-checkbox',
+    nodeIcon = 'p-tree-node-icon',
+    nodeLabel = 'p-tree-node-label',
+    nodeChildren = 'p-tree-node-children'
+}
+
 export interface TreeStyle extends BaseStyle {}