Data binding in EJ2 TypeScript Combo box control

2 Feb 202413 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.ts
index.html
import { ComboBox } from '@syncfusion/ej2-dropdowns';

// defined the array of data
let sportsData: string[] = ['Badminton', 'Cricket', 'Football', 'Golf'];

// initialize ComboBox component
let comboBoxObject: ComboBox = new ComboBox({
    //set the data to dataSource property
    dataSource: sportsData,
    // set placeholder to ComboBox input element
    placeholder: "Select a game"
});

// render initialized ComboBox
comboBoxObject.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/ej2/25.1.35/ej2-base/styles/material.css" rel="stylesheet" />
    <link href="https://cdn.syncfusion.com/ej2/25.1.35/ej2-inputs/styles/material.css" rel="stylesheet" />
    <link href="https://cdn.syncfusion.com/ej2/25.1.35/ej2-dropdowns/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>
<script src="https://cdn.syncfusion.com/ej2/syncfusion-helper.js" type ="text/javascript"></script>
</head>

<body>
    <div id='loader'>LOADING....</div>
    <div id='container' style="margin:50px auto 0; width:250px;">
        <br>
        <input type="text" tabindex="1" id='comboelement' />
    </div>
</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.ts
index.html
import { ComboBox } from '@syncfusion/ej2-dropdowns';

//define the array of complex data
let sportsData: { [key: string]: Object }[] = [
    { Id: 'Game1', Game: 'Badminton' },
    { Id: 'Game2', Game: 'Basketball' },
    { Id: 'Game3', Game: 'Cricket' },
    { Id: 'Game4', Game: 'Football' },
    { Id: 'Game5', Game: 'Golf' }
];

//initiate the ComboBox
let comboBoxObject: ComboBox = new ComboBox({
    // bind the sports Data to datasource property
    dataSource: sportsData,
    // maps the appropriate column to fields property
    fields: { text: 'Game', value: 'Id' },
    //set the placeholder to ComboBox input
    placeholder:"Select a game"
});
//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/ej2/25.1.35/ej2-base/styles/material.css" rel="stylesheet" />
    <link href="https://cdn.syncfusion.com/ej2/25.1.35/ej2-inputs/styles/material.css" rel="stylesheet" />
    <link href="https://cdn.syncfusion.com/ej2/25.1.35/ej2-dropdowns/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>
<script src="https://cdn.syncfusion.com/ej2/syncfusion-helper.js" type ="text/javascript"></script>
</head>

<body>
    <div id='loader'>LOADING....</div>
    <div id='container' style="margin:50px auto 0; width:250px;">
        <br>
        <input type="text" id='comboelement' />
    </div>
</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.ts
index.html
import { ComboBox } from '@syncfusion/ej2-dropdowns';

//define the array of complex data
let countriesData: { [key: string]: Object }[] = [
        { 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'} }
];

//initiate the ComboBox
let comboBoxObject: ComboBox = new ComboBox({
    // bind the sports Data to datasource property
    dataSource: countriesData,
    // maps the appropriate column to fields property
    fields: { text: 'Country.Name', value: 'Code.Id' },
    //set the placeholder to ComboBox input
    placeholder:"Select a country"
});
//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/ej2/25.1.35/ej2-base/styles/material.css" rel="stylesheet" />
    <link href="https://cdn.syncfusion.com/ej2/25.1.35/ej2-inputs/styles/material.css" rel="stylesheet" />
    <link href="https://cdn.syncfusion.com/ej2/25.1.35/ej2-dropdowns/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>
<script src="https://cdn.syncfusion.com/ej2/syncfusion-helper.js" type ="text/javascript"></script>
</head>

<body>
    <div id='loader'>LOADING....</div>
    <div id='container' style="margin:50px auto 0; width:250px;">
        <br>
        <input type="text" id='comboelement' />
    </div>
</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.ts
index.html
import { ComboBox } from '@syncfusion/ej2-dropdowns';
//import DataManager related classes
import { Query, DataManager, ODataV4Adaptor } from '@syncfusion/ej2-data';

//initiates the component
let customers: ComboBox = new ComboBox({
    //bind the DataManager instance to dataSource property
    dataSource: new DataManager({
            url: 'https://services.odata.org/V4/Northwind/Northwind.svc/',
            adaptor: new ODataV4Adaptor,
            crossDomain: true
        }),
    //bind the Query instance to query property
    query: new Query().from('Customers').select(['ContactName', 'CustomerID']).take(6),
    //map the appropriate columns to fields property
    fields: { text: 'ContactName', value: 'CustomerID' },
    //sort the resulted items
    sortOrder: 'Ascending',
    //set the placeholder to ComboBox input
    placeholder:"Select a customer"
});

//render the component
customers.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/ej2/25.1.35/ej2-base/styles/material.css" rel="stylesheet" />
    <link href="https://cdn.syncfusion.com/ej2/25.1.35/ej2-inputs/styles/material.css" rel="stylesheet" />
    <link href="https://cdn.syncfusion.com/ej2/25.1.35/ej2-dropdowns/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>
<script src="https://cdn.syncfusion.com/ej2/syncfusion-helper.js" type ="text/javascript"></script>
</head>

<body>
    <div id='loader'>LOADING....</div>
    <div id='container' style="margin:50px auto 0; width:250px;">
        <br>
        <input type="text" id='comboelement' />
    </div>
</body>

</html>