JavaScript/jQuery TreeView - Expand and Collapse Nodes

If a node is supposed to be expanded initially, set its expanded field to true. If another field specifies whether a node is expanded or collapsed, assign its name to the expandedExpr property as shown in the following code.

var hierarchicalData = [{
    name: 'Fruits',
    isExpanded: true,
    items: [
        { name: 'Apples' },
        { name: 'Oranges' }
    ]
}, {
    name: 'Vegetables',
    isExpanded: true,
    items: [
        { name: 'Cucumbers' },
        { name: 'Tomatoes' }
    ]
}];

$(function() {
    $("#treeViewContainer").dxTreeView({
        dataSource: hierarchicalData,
        keyExpr: 'name',
        displayExpr: 'name',
        expandedExpr: 'isExpanded'
    });
});

<dx-tree-view
    [dataSource]="hierarchicalData"
    keyExpr="name"
    displayExpr="name"
    expandedExpr="isExpanded">
</dx-tree-view>

import { DxTreeViewModule } from "devextreme-angular";
// ...
export class AppComponent {
    hierarchicalData = [{
        name: 'Fruits',
        isExpanded: true,
        items: [
            { name: 'Apples' },
            { name: 'Oranges' }
        ]
    }, {
        name: 'Vegetables',
        isExpanded: true,
        items: [
            { name: 'Cucumbers' },
            { name: 'Tomatoes' }
        ]
    }];
}
@NgModule({
    imports: [
        // ...
        DxTreeViewModule
    ],
    // ...
})

<template>
    <DxTreeView
        key-expr="key"
        display-expr="name"
        expanded-expr="isExpanded"
        :items="hierarchicalData" 
    />
</template>
<script>
import 'devextreme/dist/css/dx.light.css';

import { DxTreeView } from 'devextreme-vue/tree-view';

const hierarchicalData = [{
    key: '1',
    name: 'Fruits',
    isExpanded: true,
    items: [
        { key: '1_1', name: 'Apples' },
        { key: '1_2', name: 'Oranges' }
    ]
}, {
    key: '2',
    name: 'Vegetables',
    isExpanded: true,
    items: [
        { key: '2_1', name: 'Cucumbers' },
        { key: '2_2', name: 'Tomatoes' }
    ]
}];

export default {
    components: {
        DxTreeView
    },
    data() {
        return {
            hierarchicalData
        };
    },
};
</script>

import React from 'react';

import 'devextreme/dist/css/dx.light.css';

import TreeView from 'devextreme-react/tree-view';

const hierarchicalData = [{
    key: '1',
    name: 'Fruits',
    isExpanded: true,
    items: [
        { key: '1_1', name: 'Apples' },
        { key: '1_2', name: 'Oranges' }
    ]
}, {
    key: '2',
    name: 'Vegetables',
    isExpanded: true,
    items: [
        { key: '2_1', name: 'Cucumbers' },
        { key: '2_2', name: 'Tomatoes' }
    ]
}];

class App extends React.Component {
    render() {
        return (
            <TreeView
                keyExpr="key"
                displayExpr="name"
                expandedExpr="isExpanded"
                items={hierarchicalData} />
        );
    }
}

export default App;

The TreeView provides the following API to expand and collapse nodes:

• All nodes
  You can use the expandAll() and collapseAll() methods to expand and collapse nodes at once. Note that the expandAll() method expands only the loaded nodes if data is loaded on demand.

  jQuery

  JavaScript

  $("#treeViewContainer").dxTreeView("expandAll");
  // $("#treeViewContainer").dxTreeView("collapseAll");

  Angular

  TypeScript

  import { ..., ViewChild } from "@angular/core";
  import { DxTreeViewModule, DxTreeViewComponent } from "devextreme-angular";
  // ...
  export class AppComponent {
      @ViewChild(DxTreeViewComponent, { static: false }) treeView: DxTreeViewComponent;
      // Prior to Angular 8
      // @ViewChild(DxTreeViewComponent) treeView: DxTreeViewComponent;
      expandAllNodes () {
          this.treeView.instance.expandAll();
      }
      collapseAllNodes () {
          this.treeView.instance.collapseAll();
      }
  }
  @NgModule({
      imports: [
          // ...
          DxTreeViewModule
      ],
      // ...
  })

  Vue

  App.vue

  <template>
      <DxTreeView
          :ref="treeViewRef"
          :items="data" 
      />
  </template>
  <script>
  import 'devextreme/dist/css/dx.light.css';
  
  import { DxTreeView } from 'devextreme-vue/tree-view';
  
  const treeViewRef = 'treeView';
  const data = [ ... ];
  
  export default {
      components: {
          DxTreeView
      },
      data() {
          return {
              data,
              treeViewRef
          };
      },
      computed: {
          treeView: function() {
              return this.$refs[treeViewRef].instance;
          }
      },   
      methods: {
          expandAllNodes() {
              this.treeView.expandAll();
          },
          collapseAllNodes() {
              this.treeView.collapseAll();
          } 
      }
  };
  </script>

  React

  App.js

  import React from 'react';
  
  import 'devextreme/dist/css/dx.light.css';
  
  import TreeView from 'devextreme-react/tree-view';
  
  const data = [ ... ];
  
  class App extends React.Component {
      constructor() {
          super();
          this.treeViewRef = React.createRef();
          this.expandAllNodes = this.expandAllNodes.bind(this);
          this.collapseAllNodes = this.collapseAllNodes.bind(this);                
      }
      render() {
          return (
              <TreeView
                  items={data}
                  ref={this.treeViewRef} />
          );
      }
      expandAllNodes() {
          this.treeView.expandAll();
      }
      collapseAllNodes() {
          this.treeView.collapseAll();
      }
      get treeView() {
          return this.treeViewRef.current.instance;
      }    
  }
  
  export default App;

• Individual nodes
  Call the expandItem(key) or collapseItem(key) method and pass a node key as an argument:

  jQuery

  JavaScript

  $("#treeViewContainer").dxTreeView("expandItem", nodeKey);
  // $("#treeViewContainer").dxTreeView("collapseItem", nodeKey);

  Angular

  TypeScript

  import { ..., ViewChild } from "@angular/core";
  import { DxTreeViewModule, DxTreeViewComponent } from "devextreme-angular";
  // ...
  export class AppComponent {
      @ViewChild(DxTreeViewComponent, { static: false }) treeView: DxTreeViewComponent;
      // Prior to Angular 8
      // @ViewChild(DxTreeViewComponent) treeView: DxTreeViewComponent;
      expandNode (key) {
          this.treeView.instance.expandItem(key);
      }
      collapseNode (key) {
          this.treeView.instance.collapseItem(key);
      }
  }
  @NgModule({
      imports: [
          // ...
          DxTreeViewModule
      ],
      // ...
  })

  Vue

  App.vue

  <template>
      <DxTreeView
          :ref="treeViewRef"
          :items="data" 
      />
  </template>
  <script>
  import 'devextreme/dist/css/dx.light.css';
  
  import { DxTreeView } from 'devextreme-vue/tree-view';
  
  const treeViewRef = 'treeView';
  const data = [ ... ];
  
  export default {
      components: {
          DxTreeView
      },
      data() {
          return {
              data,
              treeViewRef
          };
      },
      computed: {
          treeView: function() {
              return this.$refs[treeViewRef].instance;
          }
      },   
      methods: {
          expandNode(key) {
              this.treeView.expandItem(key);
          },
          collapseNode(key) {
              this.treeView.collapseItem(key);
          } 
      }
  };
  </script>

  React

  App.js

  import React from 'react';
  
  import 'devextreme/dist/css/dx.light.css';
  
  import TreeView from 'devextreme-react/tree-view';
  const data = [ ... ];
  
  class App extends React.Component {
      constructor() {
          super();
          this.treeViewRef = React.createRef();
          this.expandNode = this.expandNode.bind(this);
          this.collapseNode = this.collapseNode.bind(this);
      }
      render() {
          return (
              <TreeView
                  items={data}
                  ref={this.treeViewRef} />
          );
      }
      expandNode(key) {
          this.treeView.expandItem(key);
      }
      collapseNode(key) {
          this.treeView.collapseItem(key);
      }
      get treeView() {
          return this.treeViewRef.current.instance;
      }    
  }
  
  export default App;

To execute certain commands when a node is expanded or collapsed, handle the itemExpanded or itemCollapsed event. Assign event handling functions to the onItemExpanded or onItemCollapsed property when you configure the UI component if these functions are going to remain unchanged.

$(function() {
    $("#treeViewContainer").dxTreeView({
        onItemExpanded: function (e) {
            // Handler of the "itemExpanded" event
        },
        onItemCollapsed: function (e) {
            // Handler of the "itemCollapsed" event
        }
    });
});

<dx-tree-view ...
    (onItemExpanded)="onItemExpanded($event)"
    (onItemCollapsed)="onItemCollapsed($event)">
</dx-tree-view>

import { DxTreeViewModule } from "devextreme-angular";
// ...
export class AppComponent {
    onItemExpanded (e) {
        // Handler of the "itemExpanded" event
    }
    onItemCollapsed (e) {
        // Handler of the "itemCollapsed" event
    }
}
@NgModule({
    imports: [
        // ...
        DxTreeViewModule
    ],
    // ...
})

<template>
    <DxTreeView
        :data-source="data"
        @item-expanded="onItemExpanded"
        @item-collapsed="onItemCollapsed" 
    />
</template>
<script>
import 'devextreme/dist/css/dx.light.css';

import { DxTreeView } from 'devextreme-vue/tree-view';

const data = [ ... ];

export default {
    components: {
        DxTreeView
    },
    data() {
        return {
            data
        };
    },
    methods: {
        onItemExpanded(e) {
            // Handler of the 'itemExpanded' event
        }
        onItemCollapsed(e) {
            // Handler of the 'itemCollapsed' event
        }
    }
};
</script>

import React from 'react';

import 'devextreme/dist/css/dx.light.css';

import TreeView from 'devextreme-react/tree-view';

const data = [ ... ];

class App extends React.Component {
    render() {
        return (
            <TreeView
                onItemExpanded={this.onItemExpanded}
                onItemCollapsed={this.onItemCollapsed}
                dataSource={data} />
        );
    }

    onItemExpanded(e) {
        // Handler of the 'itemExpanded' event
    }

    onItemCollapsed(e) {
        // Handler of the 'itemCollapsed' event
    }
}

export default App;

var itemCollapsedEventHandler1 = function (e) {
    // First handler of the "itemCollapsed" event
};

var itemCollapsedEventHandler2 = function (e) {
    // Second handler of the "itemCollapsed" event
};

$("#treeViewContainer").dxTreeView("instance")
    .on("itemCollapsed", itemCollapsedEventHandler1)
    .on("itemCollapsed", itemCollapsedEventHandler2);

See Also

• TreeView - Access a Node
• TreeView - Search Nodes
• TreeView Demos
• TreeView API Reference