Data binding in EJ2 JavaScript TreeView control
28 Jan 202522 minutes to read
The TreeView control provides the option to load data from either local data sources or remote data services. This can be done through the dataSource property, which is a member of the fields property. The dataSource property supports arrays 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 bandwidth usage when consuming large amounts of data. It initially loads first-level nodes, and when a parent node is expanded, it loads child nodes based on the parentID/child member.
By default, 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 is 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 the local data source. When mapper fields are not specified, it takes the default values as the mapping fields. The 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 sources that contain nested arrays 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 the fields property.
In the following example, the code, name, and countries columns from hierarchical data have been mapped to the id, text, and child fields, respectively.
ej.base.enableRipple(true);
//define the nested array of JSON objects
var continents = [
{
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' }
]
},
];
var treeObj = new ej.navigations.TreeView({
fields: { dataSource: continents, id: 'code', text: 'name', child: 'countries' }
});
treeObj.appendTo('#tree');<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="https://cdn.syncfusion.com/ej2/28.2.3/ej2-base/styles/material.css" rel="stylesheet">
<link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-navigations/styles/material.css" rel="stylesheet">
<script src="https://cdn.syncfusion.com/ej2/28.2.3/dist/ej2.min.js" type="text/javascript"></script>
<script src="https://cdn.syncfusion.com/ej2/syncfusion-helper.js" type ="text/javascript"></script>
</head>
<body>
<div id="container">
<div id="treeparent">
<div id="tree"></div>
</div>
</div>
<script>
var ele = document.getElementById('container');
if (ele) {
ele.style.visibility = "visible";
}
</script>
<script src="index.js" type="text/javascript"></script>
<style>
#treeparent {
display: block;
max-width: 350px;
max-height: 350px;
margin: auto;
overflow: auto;
border: 1px solid #dddddd;
border-radius: 3px;
}
</style>
</body>
</html>#container {
visibility: hidden;
}
#loader {
color: #008cff;
height: 40px;
width: 30%;
position: absolute;
font-family: 'Helvetica Neue', 'calibiri';
font-size: 14px;
top: 45%;
left: 45%;
}Self-referential data
TreeView can be populated from a self-referential data structure that contains an 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 the self-referential data to the fields property.
To render the root-level nodes, specify the parentID as null, or there is no need to specify the parentID in dataSource.
In the following example, the id, pid, hasChild, and name columns from self-referential data have been mapped to the id, parentID, hasChildren, and text fields, respectively.
ej.base.enableRipple(true);
var localData = [
{ 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' },
];
var treeObj = new ej.navigations.TreeView({
fields: { dataSource: localData, id: 'id', parentID: 'pid', text: 'name', hasChildren: 'hasChild' }
});
treeObj.appendTo('#tree');<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="https://cdn.syncfusion.com/ej2/28.2.3/ej2-base/styles/material.css" rel="stylesheet">
<link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-navigations/styles/material.css" rel="stylesheet">
<script src="https://cdn.syncfusion.com/ej2/28.2.3/dist/ej2.min.js" type="text/javascript"></script>
<script src="https://cdn.syncfusion.com/ej2/syncfusion-helper.js" type ="text/javascript"></script>
</head>
<body>
<div id="container">
<div id="treeparent">
<div id="tree"></div>
</div>
</div>
<script>
var ele = document.getElementById('container');
if (ele) {
ele.style.visibility = "visible";
}
</script>
<script src="index.js" type="text/javascript"></script>
<style>
#treeparent {
display: block;
max-width: 350px;
max-height: 350px;
margin: auto;
overflow: auto;
border: 1px solid #dddddd;
border-radius: 3px;
}
</style>
</body>
</html>#container {
visibility: hidden;
}
#loader {
color: #008cff;
height: 40px;
width: 30%;
position: absolute;
font-family: 'Helvetica Neue', 'calibiri';
font-size: 14px;
top: 45%;
left: 45%;
}Remote data
TreeView can also be populated from a remote data service with the help of the 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 the remote data source, you have to provide the endpoint url.
The DataManager, which acts as an interface between the service endpoint and the TreeView, requires the following information to interact with the 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.
ej.base.enableRipple(true);
var data = new ej.data.DataManager({
url: 'https://services.odata.org/V4/Northwind/Northwind.svc',
adaptor: new ej.data.ODataV4Adaptor(),
crossDomain: true,
});
var query = new ej.data.Query().from('Employees').select('EmployeeID,FirstName,Title').take(5);
var query1 = new ej.data.Query().from('Orders').select('OrderID,EmployeeID,ShipName').take(5);
var treeObj = new ej.navigations.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');<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="https://cdn.syncfusion.com/ej2/28.2.3/ej2-base/styles/material.css" rel="stylesheet">
<link href="https://cdn.syncfusion.com/ej2/28.2.3/ej2-navigations/styles/material.css" rel="stylesheet">
<script src="https://cdn.syncfusion.com/ej2/28.2.3/dist/ej2.min.js" type="text/javascript"></script>
<script src="https://cdn.syncfusion.com/ej2/syncfusion-helper.js" type ="text/javascript"></script>
</head>
<body>
<div id="container">
<div id="treeparent">
<div id="tree"></div>
</div>
</div>
<script>
var ele = document.getElementById('container');
if (ele) {
ele.style.visibility = "visible";
}
</script>
<script src="index.js" type="text/javascript"></script>
<style>
#treeparent {
display: block;
max-width: 350px;
max-height: 350px;
margin: auto;
overflow: auto;
border: 1px solid #dddddd;
border-radius: 3px;
}
</style>
</body>
</html>#container {
visibility: hidden;
}
#loader {
color: #008cff;
height: 40px;
width: 30%;
position: absolute;
font-family: 'Helvetica Neue', 'calibiri';
font-size: 14px;
top: 45%;
left: 45%;
}