Data binding in EJ2 JavaScript Combo box control

2 Feb 202414 minutes to read

The ComboBox loads the data either from local data sources or remote data services using the dataSource property. It supports the data type of array or DataManager.

The ComboBox also supports different kinds of data services such as OData, OData V4, and Web API, and data formats such as XML, JSON, and JSONP with the help of DataManager adaptors.

Fields	Type	Description
text	`string`	Specifies the display text of each list item.
value	`number or string`	Specifies the hidden data value mapped to each list item that should contain a unique value.
groupBy	`string`	Specifies the category under which the list item has to be grouped.
iconCss	`string`	Specifies the icon class of each list item.

When binding complex data to the ComboBox, fields should be mapped correctly. Otherwise, the selected item remains undefined.

Binding local data

Local data can be represented in two ways as described below.

1. Array of simple data

The ComboBox has support to load array of primitive data such as strings and numbers. Here, both value and text field act the same.

index.js
index.html
var sportsData = ['Badminton', 'Cricket', 'Football', 'Golf', 'Tennis'];
   // initialize ComboBox component
    var listObj = new ej.dropdowns.ComboBox({
        dataSource: sportsData, 
        // set placeholder to ComboBox input element
        placeholder: "Select games"});
    listObj.appendTo('#comboelement');
<!DOCTYPE html><html lang="en"><head>
    <title>EJ2 ComboBox</title>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta name="description" content="Typescript UI Controls">
    <meta name="author" content="Syncfusion">
    <link href="styles.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-base/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-inputs/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-dropdowns/styles/material.css" rel="stylesheet">
    
    
<script src="https://cdn.syncfusion.com/ej2/27.2.2/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" style="margin:50px auto 0; width:250px;">
        <br>
        <input type="text" tabindex="1" id="comboelement">
    </div>


<script>
var ele = document.getElementById('container');
if(ele) {
  ele.style.visibility = "visible";
}   
      </script>
<script src="index.js" type="text/javascript"></script>
</body></html>

2. Array of JSON data

The ComboBox can generate its list items through an array of complex data. For this, the appropriate columns should be mapped to the fields property.

In the following example, Id column and Game column from complex data have been mapped to the value field and text field, respectively.

index.js
index.html
let sportsData = [
    { Id: 'Game1', Game: 'Badminton' },
    { Id: 'Game2', Game: 'Basketball' },
    { Id: 'Game3', Game: 'Cricket' },
    { Id: 'Game4', Game: 'Football' },
    { Id: 'Game5', Game: 'Golf' },
    { Id: 'Game6', Game: 'Hockey' },
    { Id: 'Game7', Game: 'Rugby' },
    { Id: 'Game8', Game: 'Snooker' }
];
   // initialize ComboBox component
    var listObj = new ej.dropdowns.ComboBox({
      //set the data to dataSource property
        dataSource: sportsData, 
        // maps the appropriate column to fields property
        fields: { value: 'Game' },
        // set placeholder to ComboBox input element
        placeholder: "Find a game"});
    listObj.appendTo('#comboelement');
<!DOCTYPE html><html lang="en"><head>
    <title>Essential JS 2 ComboBox</title>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta name="description" content="Typescript UI Controls">
    <meta name="author" content="Syncfusion">
    <link href="styles.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-base/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-inputs/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-dropdowns/styles/material.css" rel="stylesheet">
    
    
<script src="https://cdn.syncfusion.com/ej2/27.2.2/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" style="margin:50px auto 0; width:250px;">
        <br>
        <input type="text" id="comboelement">
    </div>


<script>
var ele = document.getElementById('container');
if(ele) {
  ele.style.visibility = "visible";
}   
      </script>
<script src="index.js" type="text/javascript"></script>
</body></html>

3. Array of Complex data

The ComboBox can generate its list items through an array of complex data. For this, the appropriate columns should be mapped to the fields property.

In the following example, Code.Id column and Country.Name column from complex data have been mapped to the value field and text field, respectively.

index.js
index.html
let countriesData = [
        { Country: { Name: 'Australia' }, Code: { Id: 'AU' }},
        { Country: { Name: 'Bermuda' },Code: { Id: 'BM' }},
        { Country:{ Name: 'Canada'}, Code:{ Id: 'CA'} },
        { Country:{Name: 'Cameroon'}, Code:{ Id: 'CM'} },
        { Country:{Name: 'Denmark'}, Code:{ Id: 'DK' }},
        { Country:{Name: 'France'}, Code: { Id:'FR'} }
];
   // initialize ComboBox component
    var listObj = new ej.dropdowns.ComboBox({
      //set the data to dataSource property
        dataSource: countriesData, 
        // maps the appropriate column to fields property
        fields: { value: 'Country.Name' },
        // set placeholder to ComboBox input element
        placeholder: "Find a country"});
    listObj.appendTo('#comboelement');
<!DOCTYPE html><html lang="en"><head>
    <title>Essential JS 2 ComboBox</title>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta name="description" content="Typescript UI Controls">
    <meta name="author" content="Syncfusion">
    <link href="styles.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-base/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-inputs/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-dropdowns/styles/material.css" rel="stylesheet">
    
    
<script src="https://cdn.syncfusion.com/ej2/27.2.2/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" style="margin:50px auto 0; width:250px;">
        <br>
        <input type="text" id="comboelement">
    </div>


<script>
var ele = document.getElementById('container');
if(ele) {
  ele.style.visibility = "visible";
}   
      </script>
<script src="index.js" type="text/javascript"></script>
</body></html>

Binding remote data

The ComboBox supports retrieval of data from remote data services with the help of DataManager component. The Query property is used to fetch data from the database and bind it to the ComboBox.

In the following sample, displayed first 6 contacts from the customer table of Northwind Data Service.

index.js
index.html
//initiates the component
var comboBoxObject = new ej.dropdowns.ComboBox({
    //bind the data manager instance to dataSource property
    dataSource: new ej.data.DataManager({
            url: 'https://services.odata.org/V4/Northwind/Northwind.svc/',
            adaptor: new ej.data.ODataV4Adaptor(),
            crossDomain: true
    }),
    //bind the Query instance to query property
    query: new ej.data.Query().from('Employees').select(['FirstName', 'City','EmployeeID']).take(6),
    //map the appropriate columns to fields property
    fields: { value: 'FirstName' },
    //set the placeholder to ComboBox input
    placeholder:"Select an employee",
    //sort the resulted items
    sortOrder: 'Ascending'
});

//render the component
comboBoxObject.appendTo('#comboelement');
<!DOCTYPE html><html lang="en"><head>
    <title>Essential JS 2 ComboBox</title>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta name="description" content="Typescript UI Controls">
    <meta name="author" content="Syncfusion">
    <link href="styles.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-base/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-inputs/styles/material.css" rel="stylesheet">
    <link href="https://cdn.syncfusion.com/ej2/27.2.2/ej2-dropdowns/styles/material.css" rel="stylesheet">
    
    
<script src="https://cdn.syncfusion.com/ej2/27.2.2/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" style="margin:50px auto 0; width:250px;">
        <br>
        <input type="text" id="comboelement">
    </div>


<script>
var ele = document.getElementById('container');
if(ele) {
  ele.style.visibility = "visible";
}   
      </script>
<script src="index.js" type="text/javascript"></script>
</body></html>