Configuration

An object defining configuration options for the TreeView widget.

accessKey

Specifies the shortcut key that sets focus on the widget.

Type: String
Default Value: null

The value of this option will be passed to the accesskey attribute of the HTML element that underlies the widget.

activeStateEnabled

Specifies whether or not the widget changes its state when interacting with a user.

Type: Boolean
Default Value: false

This option is used when the widget is displayed on a platform whose guidelines include the active state change for widgets.

animationEnabled

Specifies whether or not to animate item collapsing and expanding.

Type: Boolean
Default Value: true

Show Example:
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createChildren

Allows you to load nodes manually.

Type: function
Function parameters:
parentNode: TreeView Node
The node that has been expanded; null for the root node.
Return Value: jQuery.Promise|Array
A Promise of a Deferred object resolved with the result from the server or an array of objects to be converted to child nodes.

If you have a large data source hosted remotely, loading all of it may take considerable time. To quicken the process, you can load data for an individual node using the createChildren function. This function will be called at the beginning of the widget's lifetime and each time a user expands a node whose child nodes have not been loaded yet.

In the following code, the createChildren function makes a query to the server passing the parentNode object. The structure of this object is described in the Node section.

JavaScript
$(function() {
    $("#treeViewContainer").dxTreeView({
        createChildren: function (parentNode) {
            var d = $.Deferred();
            $.get("http://url/to/the/service", parentNode).done(function (result) {
                d.resolve(result);
            });
            return d.promise();
        },
        dataStructure: 'plain'
    });
});
NOTE
The createChildren function applies only if the dataStructure option is set to "plain" and the dataSource option is unspecified.

View Demo

See Also

dataSource

A data source used to fetch data to be displayed by the widget.

Default Value: null

This option accepts one of the following.

  • Array of objects
    A simple JavaScript array containing a collection of plain objects.

  • URL
    A URL to JSON data or to a service returning data in JSON format.

  • DataSource or its configuration object
    A DataSource is an object that provides a handy API for data processing. A DataSource is a stateful object, which means that it saves data processing settings and applies them each time data is loaded. All underlying data access logic of a DataSource is isolated in a Store. A Store provides an API for reading and modifying data. Unlike the DataSource, a Store is a stateless object.

NOTE
The widget requires each data item to have a key field whose value is unique within the entire array.
NOTE
If the data source is specified using the dataSource option, use the items option only for reading. Updating data items using the items option may cause unexpected results.

To display widget items, a default template can be used. This template is based on the data source fields that are listed in the Default Item Template section of the widget's API. Alternatively, you can implement a custom item template. For details, refer to the Customize Node Appearance topic.

See Also

dataStructure

Specifies whether a nested or plain array is used as a data source.

Type: String
Default Value: 'tree'
Accepted Values: 'tree' | 'plain'

If the option is set to 'tree', the array should have a tree structure. This means that each item can contain the items field, which contains an array of nested items.

JavaScript
var treeViewData = [
    {
        id: 1,
        items: [
            { id: 11 },
            { id: 12 },
            { 
                id: 13,
                items: [
                    { id: 131 },
                    { id: 132 },
                    { id: 133 },
                ]
            },
        ]
    },
    { id: 2 }
];

If the dataStructure option value is 'plain', the array should have a plain structure. In this case, each array item should contain the parentId field, which specifies the key of the parent item.

JavaScript
var treeViewData = [
    { id: 1, parentId: 0 },
    { id: 11, parentId: 1 },
    { id: 12, parentId: 1 },
    { id: 13, parentId: 1 },
    { id: 131, parentId: 13 },
    { id: 132, parentId: 13 },
    { id: 133, parentId: 13 },
    { id: 2, parentId: 0 }
];
NOTE
If the dataStructure option is set to 'plain', the widget requires you to specify at least one root item. An item is used as a root item if its parentId field holds 0 or null.
NOTE
The widget requires each data item to have a key field whose value is unique within the entire array.

When using the widget as an ASP.NET MVC Control, specify this option using the TreeViewDataStructure enum. This enum accepts the following values: Plain and Tree.

See Also
Show Example:
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disabled

Specifies whether the widget responds to user interaction.

Type: Boolean
Default Value: false

disabledExpr

Specifies the name of the data source item field whose value defines whether or not the corresponding widget item is disabled.

Type: String| function
Default Value: 'disabled'

displayExpr

Specifies the name of the data source item field whose value is displayed by the widget.

Type: String| function
Default Value: 'text'

elementAttr

Specifies the attributes to be attached to the widget's root element.

Type: Object
Default Value: {}

When you configure this option in an ASP.NET MVC Control, pass a dictionary as shown in the following code.

Razor C#
Razor VB
@(Html.DevExtreme()
    // other widget options
    // ...
    .ElementAttr(new Dictionary<string, object>() {
        { "id", "elementId" },
        { "class", "class-name" },
        // ...
    })
)
@(Html.DevExtreme().WidgetName() _
    .ElementAttr(New Dictionary(Of String, Object) From {
        { "id", "elementId" },
        { "class", "class-name" }
    })
)

expandAllEnabled

Specifies whether or not a user can expand all tree view items by the "*" hot key.

Type: Boolean
Default Value: false

Show Example:
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expandedExpr

Specifies the name of the data source item field whose value defines whether or not the corresponding widget item is displayed expanded.

Type: String| function
Default Value: 'expanded'

expandNodesRecursive

Specifies whether or not all parent nodes of an initially expanded node are displayed expanded.

Type: Boolean
Default Value: true

focusStateEnabled

Specifies whether the widget can be focused using keyboard navigation.

Type: Boolean
Default Value: false
Default for desktop: true

hasItemsExpr

Specifies the name of the data source item field whose value defines whether or not the corresponding node includes child nodes.

Type: String| function
Default Value: 'hasItems'

height

Specifies the height of the widget.

Type: Number|String| function
Return Value: Number|String
The height of the widget.
Default Value: undefined

This option accepts a value of one of the following types.

  • Number
    The height of the widget in pixels.

  • String
    A CSS-accepted measurement of height. For example, "55px", "80%", "auto", "inherit".

  • Function
    A function returning either of the above. For example:

    JavaScript
    height: function() {
        return window.innerHeight / 1.5;
    }

hint

Specifies text for a hint that appears when a user pauses on the widget.

Type: String
Default Value: undefined

hoverStateEnabled

Specifies whether the widget changes its state when a user pauses on it.

Type: Boolean
Default Value: true

itemHoldTimeout

The time period in milliseconds before the onItemHold event is raised.

Type: Number
Default Value: 750

items

An array of items displayed by the widget.

Type: Array
NOTE
The widget requires each data item to have a key field whose value is unique within the entire array.

You can use the dataSource option instead. Unlike the items option, the dataSource option can take on the DataSource configuration object as well as a simple array.

NOTE
If you need to modify the data source specified using the items option at runtime, do it only with the help of the items option. Updating data items using the dataSource option may cause unexpected results.

To display widget items, a default template can be used. This template is based on the data source fields that are listed in the Default Item Template section of the widget's API. Alternatively, you can implement a custom item template. For details, refer to the Customize Node Appearance topic.

itemsExpr

Specifies the name of the data source item field that contains an array of nested items.

Type: String| function
Default Value: 'items'

This option is used if the dataStructure option value is 'tree'.

itemTemplate

The template to be used for rendering items.

Type: template
Function parameters:
itemData: Object
The item object to be rendered.
itemIndex: Number
The index of the item to be rendered.
itemElement: jQuery
An HTML element of the item to be rendered.
Return Value: String|DOM Node|jQuery
A template name or a template container.
Default Value: 'item'

A binding context of an item template is the data source object that corresponds to the currently rendered item.

In Knockout approach, you can bind template elements to the item object's fields directly. To access another binding context within an item template, use Knockout binding variables.

In AngularJS Approach, if you need to access item object's fields within a template, use a variable whose name is assigned to the dx-item-alias directive. Add the directive to the widget element to specify an alias to the root object of an item. Without this directive, item object fields are beyond reach. To access another binding context within an item template, use AngularJS binding variables.

See Also

keyExpr

Specifies which data field provides keys for TreeView items.

Type: String| function
Default Value: 'id'
NOTE
The key value should be unique within the data array.
See Also

noDataText

The text or HTML markup displayed by the widget if the item collection is empty.

Type: String
Default Value: 'No data to display'

onContentReady

A handler for the contentReady event. Executed when the widget's content is ready. This handler may be executed multiple times during the widget's lifetime depending on the number of times its content changes.

Type: function
Function parameters:
Information about the event.
Object structure:
component: Object
The widget's instance.
element: jQuery
The widget's container.
model: Object
The model data. Available only when using Knockout.
Default Value: null

onDisposing

A handler for the disposing event. Executed when the widget is removed from the DOM using the remove(), empty(), or html() jQuery methods only.

Type: function
Function parameters:
Information about the event.
Object structure:
component: Object
The widget instance.
element: jQuery
The widget's container.
model: Object
The model data. Available only if you use Knockout.
Default Value: null

onInitialized

A handler for the initialized event. Executed only once, after the widget is initialized.

Type: function
Function parameters:
Information about the event.
Object structure:
component: Object
The widget instance.
element: jQuery
The widget's container.
Default Value: null

You cannot access elements in the widget because this handler is executed before they are ready. Use the onContentReady handler instead.

onItemClick

A handler for the itemClick event.

Type: function
Function parameters:
Provides function parameters.
Object structure:
component: Object
Provides access to the widget instance.
element: jQuery
An HTML element of the widget.
model: Object
Provides access to the data that is available for binding against the element. Available only in the Knockout approach.
itemData: Object
The data that is bound to the clicked item.
itemElement: jQuery
An HTML element of the item.
itemIndex: Number
Specifies the index of the clicked item.
The item node.
Default Value: null

Assign a function to perform a custom action when a widget item is clicked.

To navigate to a specific URL when the itemClick event fires, assign that URL or the anchor part (#) of that URL directly to this option as a string.

onItemCollapsed

A handler for the itemCollapsed event.

Type: function
Function parameters:
Provides function parameters.
Object structure:
component: Object
Provides access to the widget instance.
element: jQuery
An HTML element of the widget.
model: Object
Provides access to the data that is available for binding against the element. Available only in the Knockout approach.
itemData: Object
The data that is bound to the clicked item.
itemElement: jQuery
An HTML element of the item.
itemIndex: Number
Specifies the index of the collapsed item.
jQueryEvent: jQuery.Event
Specifies the jQuery event that caused action execution.
The collapsed item node.
Default Value: null

Assign a function to perform a custom action when a tree view item is collapsed.

onItemContextMenu

A handler for the itemContextMenu event.

Type: function
Function parameters:
Provides function parameters.
Object structure:
component: Object
Provides access to the widget instance.
element: jQuery
An HTML element of the widget.
model: Object
Provides access to the data that is available for binding against the element. Available only in the Knockout approach.
itemData: Object
The data that is bound to the item.
itemElement: jQuery
An HTML element of the item.
itemIndex: Number
Specifies the index of the item.
jQueryEvent: jQuery.Event
Specifies the jQuery event that caused action execution.
The item node.
Default Value: null

Assign a function to perform a custom action when the right mouse button is clicked when the pointer is over a widget item, or when the "sustained" (also known as a long press) touch action is performed.

onItemExpanded

A handler for the itemExpanded event.

Type: function
Function parameters:
Provides function parameters.
Object structure:
component: Object
Provides access to the widget instance.
element: jQuery
An HTML element of the widget.
model: Object
Provides access to the data that is available for binding against the element. Available only in the Knockout approach.
itemData: Object
The data that is bound to the expanded item.
itemElement: jQuery
An HTML element of the item.
itemIndex: Number
Specifies the index of the expanded item.
jQueryEvent: jQuery.Event
Specifies the jQuery event that caused action execution.
The expanded item node.
Default Value: null

Assign a function to perform a custom action when a tree view item is expanded.

onItemHold

A handler for the itemHold event.

Type: function
Function parameters:
Provides function parameters.
Object structure:
component: Object
Provides access to the widget instance.
element: jQuery
An HTML element of the widget.
model: Object
Provides access to the data that is available for binding against the element. Available only in the Knockout approach.
itemData: Object
The data that is bound to the item being held.
itemElement: jQuery
An HTML element of the item.
itemIndex: Number
Specifies the index of the item being held.
The item node.
Default Value: null

Assign a function to perform a custom action when the widget's collection item is being held for a specified time period (see the itemHoldTimeout option).

onItemRendered

A handler for the itemRendered event.

Type: function
Function parameters:
Provides function parameters.
Object structure:
component: Object
Provides access to the widget instance.
element: jQuery
An HTML element of the widget.
model: Object
Provides access to the data that is available for binding against the element. Available only in the Knockout approach.
itemData: Object
The data that is bound to the item to be rendered.
itemElement: jQuery
An HTML element of the item.
itemIndex: Number
Specifies the index of the rendered item.
The item node.
Default Value: null

Assign a function to perform a custom action after a collection item is rendered.

onItemSelected

Deprecated

Use the onItemSelectionChanged option instead.

A handler for the itemSelected event.

Type: function
Function parameters:
Provides function parameters.
Object structure:
component: Object
Provides access to the widget instance.
element: jQuery
An HTML element of the widget.
model: Object
Provides access to the data that is available for binding against the element. Available only in the Knockout approach.
A node of the selected item.
Default Value: null

Assign a function to perform a custom action when a tree view item is selected.

View Demo

onItemSelectionChanged

A handler for the itemSelectionChanged event.

Type: function
Function parameters:
Provides function parameters.
Object structure:
component: Object
Provides access to the widget instance.
element: jQuery
An HTML element of the widget.
model: Object
Provides access to the data that is available for binding against the element. Available only in the Knockout approach.
A node of the selected item.
Default Value: null

This option makes sense in one of the following cases.

  1. The selectByClick option is set to true.
  2. The showCheckBoxesMode option is not set to 'none'.
  3. You use one of the methods: selectAll, unselectAll, selectItem, unselectItem.

View Demo

onOptionChanged

A handler for the optionChanged event. Executed after an option of the widget is changed.

Type: function
Function parameters:
Information about the event.
Object structure:
component: Object
The widget instance.
name: String
A short name of the option whose value has been changed.
fullName: String
A full name of the option whose value has been changed; contains a full hierarchy of the option.
value: any
A new value for the option.
element: jQuery
The widget's container.
model: Object
The model data. Available only if you use Knockout.
Default Value: null

onSelectionChanged

A handler for the selectionChanged event.

Type: function
Function parameters:
Provides function parameters.
Object structure:
component: Object
Provides access to the widget instance.
element: jQuery
An HTML element of the widget.
model: Object
Provides access to the data that is available for binding against the element. Available only in the Knockout approach.
Default Value: null

Assign a function to perform a custom action when the selection changes.

This option makes sense in one of the following cases.

  1. The selectByClick option is set to true.
  2. The showCheckBoxesMode option is not set to 'none'.
  3. You use one of the methods: selectAll, unselectAll, selectItem, unselectItem.

parentIdExpr

Specifies the name of the data source item field for holding the parent key of the corresponding node.

Type: String| function
Default Value: 'parentId'

This option is used if the dataStructure option is set to 'plain'.

View Demo

rootValue

Specifies the parent ID value of the root item.

Type: Object
Default Value: 0

rtlEnabled

Switches the widget to a right-to-left representation.

Type: Boolean
Default Value: false

When this option is set to true, the widget text flows from right to left, and the layout of elements is reversed. To switch the entire application/site to the right-to-left representation, assign true to the rtlEnabled field of the object passed to the DevExpress.config(config) method.

JavaScript
DevExpress.config({
    rtlEnabled: true
});

scrollDirection

A string value specifying available scrolling directions.

Type: String
Default Value: 'vertical'
Accepted Values: 'vertical' | 'horizontal' | 'both'

When using the widget as an ASP.NET MVC Control, specify this option using the ScrollDirection enum. This enum accepts the following values: Vertical, Horizontal and Both.

searchValue

Specifies the current value used to filter tree view items.

Type: String
Default Value: ''

If this option holds a non-empty string, the tree view displays only items containing this string and their parent items.

NOTE
When the virtual mode is enabled, the TreeView filters only the currently loaded items.
Show Example:
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selectAllEnabled

Deprecated

Use the showCheckBoxesMode options instead.

Specifies whether the "Select All" check box is displayed over the tree view.

Type: Boolean
Default Value: false

Use this option only if the showCheckBoxes option value is true.

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selectAllText

Specifies the text displayed at the "Select All" check box.

Type: String
Default Value: 'Select All'

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selectByClick

Specifies whether or not an item becomes selected if a user clicks it.

Type: Boolean
Default Value: false

selectedExpr

Specifies the name of the data source item field whose value defines whether or not the corresponding widget items is selected.

Type: String| function
Default Value: 'selected'

selectionMode

Specifies item selection mode.

Type: String
Default Value: 'multiple'
Accepted Values: 'single' | 'multiple'

When using the widget as an ASP.NET MVC Control, specify this option using the NavSelectionMode enum. This enum accepts the following values: Single and Multiple.

selectNodesRecursive

Specifies whether or not to select nodes recursively.

Type: Boolean
Default Value: true

If this option is enabled, the widget selects (unselects) all child nodes if a user selects (unselects) the parent node.

Show Example:
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showCheckBoxes

Deprecated

Use the showCheckBoxesMode options instead.

Specifies whether or not a check box is displayed at each tree view item.

Type: Boolean
Default Value: false
Show Example:
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showCheckBoxesMode

Specifies the current check boxes display mode.

Type: String
Default Value: 'none'
Accepted Values: 'none' | 'normal' | 'selectAll'

The option accepts the following values.

  • 'none'
    The widget does not display check boxes.

  • 'normal'
    The widget displays a check box for each item.

  • 'selectAll'
    The widget displays a check box for each item and the 'select all' check box at the top of the widget.

When using the widget as an ASP.NET MVC Control, specify this option using the TreeViewCheckBoxMode enum. This enum accepts the following values: None, Normal and SelectAll.

View Demo

tabIndex

Specifies the number of the element when the Tab key is used for navigating.

Type: Number
Default Value: 0

The value of this option will be passed to the tabindex attribute of the HTML element that underlies the widget.

virtualModeEnabled

Specifies if the virtual mode is enabled.

Type: Boolean
Default Value: false

If the option is set to true, the widget initially loads only root items. Child items are loaded when their parent is being expanded.

NOTE
You can use the virtual mode only if the dataSource option holds the DataSource instance able to filter items by parent ID, and the dataStructure option is set to "plain". Otherwise, the virtualModeEnabled option is ignored.

Use this option to improve the widget performance when working with a huge data source.

View Demo

See Also

visible

Specifies whether the widget is visible.

Type: Boolean
Default Value: true

width

Specifies the width of the widget.

Type: Number|String| function
Return Value: Number|String
The width of the widget.
Default Value: undefined

This option accepts a value of one of the following types.

  • Number
    The width of the widget in pixels.

  • String
    A CSS-accepted measurement of width. For example, "55px", "80%", "auto", "inherit".

  • Function
    A function returning either of the above. For example:

    JavaScript
    width: function() {
        return window.innerWidth / 1.5;
    }