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Data Binding

The TreeView control provides the option to load data either from local data sources or from remote data services. This can be done through dataSource property that is a member of the fields property. The dataSource property supports array of JavaScript objects and DataManager. It also supports different kinds of data services such as OData, OData V4, Web API, URL, and JSON with the help of DataManager adaptors.

TreeView has load on demand (Lazy load), by default. It reduces the bandwidth size when consuming huge data. It loads first level nodes initially, and when parent node is expanded, loads the child nodes based on the parentID/child member.

By default, the loadOnDemand is set to true. By disabling this property, all the tree nodes are rendered at the beginning itself.

You can use the dataBound event to perform actions. This event will be triggered once the data source is populated in the TreeView.

Local data

To bind local data to the TreeView, you can assign a JavaScript object array to the dataSource property. The TreeView control requires three fields (ID, text, and parentID) to render local data source. When mapper fields are not specified, it takes the default values as the mapping fields. Local data source can also be provided as an instance of the DataManager. It supports two kinds of local data binding methods.

  • Hierarchical data

  • Self-referential data

Hierarchical data

TreeView can be populated with hierarchical data source that contains nested array of JSON objects. You can directly assign hierarchical data to the dataSource property, and map all the field members with corresponding keys from the hierarchical data to fields property.

In the following example, code, name, and countries columns from hierarchical data have been mapped to id, text, and child fields, respectively.

Source
Preview
index.ts
index.html
import { enableRipple } from '@syncfusion/ej2-base';
enableRipple(true);
import { TreeView } from '@syncfusion/ej2-navigations';

//define the nested array of JSON objects
let continents: { [key: string]: Object; }[] = [
    {
        code: 'AF', name: 'Africa', countries: [
            { code: 'NGA', name: 'Nigeria' },
            { code: 'EGY', name: 'Egypt' },
            { code: 'ZAF', name: 'South Africa' }
        ]
    },
    {
        code: 'AS', name: 'Asia', expanded: true, countries: [
            { code: 'CHN', name: 'China' },
            { code: 'IND', name: 'India', selected: true },
            { code: 'JPN', name: 'Japan' }
        ]
    },
    {
        code: 'EU', name: 'Europe', countries: [
            { code: 'DNK', name: 'Denmark' },
            { code: 'FIN', name: 'Finland' },
            { code: 'AUT', name: 'Austria' }
        ]
    },
    {
        code: 'NA', name: 'North America', countries: [
            { code: 'USA', name: 'United States of America' },
            { code: 'CUB', name: 'Cuba' },
            { code: 'MEX', name: 'Mexico' }
        ]
    },
    {
        code: 'SA', name: 'South America', countries: [
            { code: 'BRA', name: 'Brazil' },
            { code: 'COL', name: 'Colombia' },
            { code: 'ARG', name: 'Argentina' }
        ]
    },
    {
        code: 'OC', name: 'Oceania', countries: [
            { code: 'AUS', name: 'Australia' },
            { code: 'NZL', name: 'New Zealand' },
            { code: 'WSM', name: 'Samoa' }
        ]
    },
    {
        code: 'AN', name: 'Antarctica', countries: [
            { code: 'BVT', name: 'Bouvet Island' },
            { code: 'ATF', name: 'French Southern Lands' }
        ]
    },
];


let treeObj: TreeView = new TreeView({
    fields: { dataSource: continents, id: 'code', text: 'name', child: 'countries' }
});
treeObj.appendTo('#tree');
<!DOCTYPE html>
<html lang="en">

<head>
    <title>Essential JS 2 for TreeView </title>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta name="description" content="Essential JS 2 for TreeView UI Control" />
    <meta name="author" content="Syncfusion" />
    <link href="index.css" rel="stylesheet" />
    <link href="//cdn.syncfusion.com/ej2/ej2-base/styles/material.css" rel="stylesheet" />
    <link href="//cdn.syncfusion.com/ej2/ej2-navigations/styles/material.css" rel="stylesheet" />
    <script src="https://cdnjs.cloudflare.com/ajax/libs/systemjs/0.19.38/system.js"></script>
    <script src="systemjs.config.js"></script>
</head>

<body>
    <div id='loader'>Loading....</div>
    <div id='container'>
        <div id='treeparent'>
            <div id="tree"></div>
        </div>
    </div>
</body>

</html>

Self-referential data

TreeView can be populated from self-referential data structure that contains array of JSON objects with parentID mapping.

You can directly assign self-referential data to the dataSource property, and map all the field members with corresponding keys from self-referential data to fields property.

To render the root level nodes, specify the parentID as null or no need to specify the parentID in dataSource.

In the following example, id, pid, hasChild, and name columns from self-referential data have been mapped to id, parentID, hasChildren, and text fields, respectively.

Source
Preview
index.ts
index.html
import { enableRipple } from '@syncfusion/ej2-base';
enableRipple(true);
import { TreeView } from '@syncfusion/ej2-navigations';

let localData: { [key: string]: Object }[] = [
    { id: 1, name: 'Discover Music', hasChild: true, expanded: true },
    { id: 2, pid: 1, name: 'Hot Singles' },
    { id: 3, pid: 1, name: 'Rising Artists' },
    { id: 4, pid: 1, name: 'Live Music' },
    { id: 6, pid: 1, name: 'Best of 2017 So Far' },
    { id: 7, name: 'Sales and Events', hasChild: true },
    { id: 8, pid: 7, name: '100 Albums - $5 Each' },
    { id: 9, pid: 7, name: 'Hip-Hop and R&B Sale' },
    { id: 10, pid: 7, name: 'CD Deals' },
    { id: 11, name: 'Categories', hasChild: true },
    { id: 12, pid: 11, name: 'Songs' },
    { id: 13, pid: 11, name: 'Bestselling Albums' },
    { id: 14, pid: 11, name: 'New Releases' },
    { id: 15, pid: 11, name: 'Bestselling Songs' },
    { id: 16, name: 'MP3 Albums', hasChild: true },
    { id: 17, pid: 16, name: 'Rock' },
    { id: 18, pid: 16, name: 'Gospel' },
    { id: 19, pid: 16, name: 'Latin Music' },
    { id: 20, pid: 16, name: 'Jazz' },
    { id: 21, name: 'More in Music', hasChild: true },
    { id: 22, pid: 21, name: 'Music Trade-In' },
    { id: 23, pid: 21, name: 'Redeem a Gift Card' },
    { id: 24, pid: 21, name: 'Band T-Shirts' },
];

let treeObj: TreeView = new TreeView({
    fields: { dataSource: localData, id: 'id', parentID: 'pid', text: 'name', hasChildren: 'hasChild' }
});
treeObj.appendTo('#tree');
<!DOCTYPE html>
<html lang="en">

<head>
    <title>Essential JS 2 for TreeView </title>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta name="description" content="Essential JS 2 for TreeView UI Control" />
    <meta name="author" content="Syncfusion" />
    <link href="index.css" rel="stylesheet" />
    <link href="//cdn.syncfusion.com/ej2/ej2-base/styles/material.css" rel="stylesheet" />
    <link href="//cdn.syncfusion.com/ej2/ej2-navigations/styles/material.css" rel="stylesheet" />
    <script src="https://cdnjs.cloudflare.com/ajax/libs/systemjs/0.19.38/system.js"></script>
    <script src="systemjs.config.js"></script>
</head>

<body>
    <div id='loader'>Loading....</div>
    <div id='container'>
        <div id='treeparent'>
            <div id="tree"></div>
        </div>
    </div>
</body>

</html>

Remote data

TreeView can also be populated from a remote data service with the help of DataManager control and Query property.

It supports different kinds of data services such as OData, OData V4, Web API, URL, and JSON with the help of DataManager adaptors.

You can assign service data as an instance of DataManager to the dataSource property. To interact with remote data source, you have to provide the endpoint url.

The DataManager that acts as an interface between the service endpoint and the TreeView requires the following information to interact with service endpoint properly.

  • DataManager->url: Defines the service endpoint to fetch data.

  • DataManager->adaptor: Defines the adaptor option. By default, ODataAdaptor is used for remote binding.

Adaptor is responsible for processing response and request from/to the service endpoint. The @syncfusion/ej2-data package provides some predefined adaptors designed to interact with service endpoints. They are,

  • UrlAdaptor: Used to interact with remote services. This is the base adaptor for all remote based adaptors.

  • ODataAdaptor: Used to interact with OData endpoints.

  • ODataV4Adaptor: Used to interact with OData V4 endpoints.

  • WebApiAdaptor: Used to interact with Web API created under OData standards.

  • WebMethodAdaptor: Used to interact with web methods.

In the following example, ODataV4Adaptor is used to fetch data from remote services. The EmployeeID, FirstName, and EmployeeID columns from Employees table have been mapped to id, text, and hasChildren fields respectively for first level nodes.

The OrderID, EmployeeID, and ShipName columns from orders table have been mapped to id, parentID, and text fields respectively for second level nodes.

Source
Preview
index.ts
index.html
import { enableRipple } from '@syncfusion/ej2-base';
enableRipple(true);
import { TreeView } from '@syncfusion/ej2-navigations';
//import data manager related classes
import { Query, DataManager, ODataAdaptor } from '@syncfusion/ej2-data';

let data: DataManager = new DataManager({
    url: 'https://js.syncfusion.com/demos/ejServices/Wcf/Northwind.svc',
    adaptor: new ODataAdaptor,
    crossDomain: true,
});
let query: Query = new Query().from('Employees').select('EmployeeID,FirstName,Title').take(5);
let query1: Query = new Query().from('Orders').select('OrderID,EmployeeID,ShipName').take(5);

let treeObj: TreeView = new TreeView({
    fields: { dataSource: data, query: query, id: 'EmployeeID', text: 'FirstName', hasChildren: 'EmployeeID', tooltip: 'Title',
        child: { dataSource: data, query: query1, id: 'OrderID', parentID: 'EmployeeID', text: 'ShipName' }
    }
});
treeObj.appendTo('#tree');
<!DOCTYPE html>
<html lang="en">

<head>
    <title>Essential JS 2 for TreeView </title>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta name="description" content="Essential JS 2 for TreeView UI Control" />
    <meta name="author" content="Syncfusion" />
    <link href="index.css" rel="stylesheet" />
    <link href="//cdn.syncfusion.com/ej2/ej2-base/styles/material.css" rel="stylesheet" />
    <link href="//cdn.syncfusion.com/ej2/ej2-navigations/styles/material.css" rel="stylesheet" />
    <script src="https://cdnjs.cloudflare.com/ajax/libs/systemjs/0.19.38/system.js"></script>
    <script src="systemjs.config.js"></script>
</head>

<body>
    <div id='loader'>Loading....</div>
    <div id='container'>
        <div id='treeparent'>
            <div id="tree"></div>
        </div>
    </div>
</body>

</html>