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Filtering in JavaScript DropDownList control

The DropDownList has built-in support to filter data items when allowFiltering is enabled. The filter operation starts as soon as you start typing characters in the search box.

To display filtered items in the popup, filter the required data and return it to the DropDownList via updateData method by using the filtering event.

The following sample illustrates how to query the data source and pass the data to the DropDownList through the updateData method in filtering event.

Source
Preview
app.ts
index.html
import { DropDownList, FilteringEventArgs } from '@syncfusion/ej2-dropdowns';
import { DataManager, Query } from '@syncfusion/ej2-data';

let searchData: { [key: string]: Object; }[] = [
{ Index: "s1", Country: "Alaska" }, { Index: "s2", Country: "California" },
{ Index: "s3", Country: "Florida" }, { Index: "s4", Country: "Georgia" }
];
let filter: DropDownList = new DropDownList({
    dataSource: searchData,
    // map the appropriate column
    fields: { text: "Country", value: "Index" },
    // set placeholder to DropDownList input element
    placeholder:"Select a country",
    // set true to allowFiltering for enable filtering supports
    allowFiltering: true,
    //Bind the filter event
    filtering: function (e: FilteringEventArgs) {
        let query = new Query();
        //frame the query based on search string with filter type.
        query = (e.text != "") ? query.where("Country", "startswith", e.text, true) : query;
        //pass the filter data source, filter query to updateData method.
        e.updateData(searchData, query);
    }
});
filter.appendTo('#ddlelement');
<!DOCTYPE html>
<html lang="en">

<head>
    <title>Essential JS 2 DropDownList</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="//cdn.syncfusion.com/ej2/ej2-base/styles/material.css" rel="stylesheet" />
    <link href="//cdn.syncfusion.com/ej2/ej2-inputs/styles/material.css" rel="stylesheet" />
    <link href="//cdn.syncfusion.com/ej2/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>
</head>

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

</html>

Limit the minimum filter character

When filtering the list items, you can set the limit for character count to raise remote request and fetch filtered data on the DropDownList. This can be done by manual validation within the filter event handler.

In the following example, the remote request does not fetch the search data until the search key contains three characters.

Source
Preview
app.ts
index.html
import { DropDownList, FilteringEventArgs } from '@syncfusion/ej2-dropdowns';
import { Query, DataManager, ODataV4Adaptor } from '@syncfusion/ej2-data';
let searchData: DataManager = new DataManager({
            url: 'https://services.odata.org/V4/Northwind/Northwind.svc/Customers',
            adaptor: new ODataV4Adaptor,
            crossDomain: true
});
let filter: DropDownList = new DropDownList({
    dataSource: searchData,
    query: new Query().select(['ContactName', 'CustomerID']).take(7),
    // map the appropriate column
    fields: { text: 'ContactName', value: 'CustomerID' },
    // set placeholder to DropDownList input element
    placeholder:"Select a name",
    //sort the resulted items
    sortOrder: 'Ascending',
    // set true to allowFiltering for enable filtering supports
    allowFiltering: true,
    //bind the filtering event handler
    filtering: (e: FilteringEventArgs) => {
        // load overall data when search key empty.
        if(e.text == '') e.updateData(searchData);
        else{
           // restrict the remote request until search key contains 3 characters.
          if (e.text.length < 3) { return; }
          let query: Query = new Query().select(['ContactName', 'CustomerID']);
          query = (e.text !== '') ? query.where('ContactName', 'startswith', e.text, true) : query;
          e.updateData(searchData, query);
        }
    }
});
filter.appendTo('#ddlelement');
<!DOCTYPE html>
<html lang="en">

<head>
    <title>Essential JS 2 DropDownList</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="//cdn.syncfusion.com/ej2/ej2-base/styles/material.css" rel="stylesheet" />
    <link href="//cdn.syncfusion.com/ej2/ej2-inputs/styles/material.css" rel="stylesheet" />
    <link href="//cdn.syncfusion.com/ej2/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>
</head>

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

</html>

Change the filter type

While filtering, you can change the filter type to contains, startsWith, or endsWith for string type within the filter event handler.

In the following examples, data filtering is done with endsWith type.

Source
Preview
app.ts
index.html
import { DropDownList, FilteringEventArgs } from '@syncfusion/ej2-dropdowns';
import { Query, DataManager, ODataV4Adaptor } from '@syncfusion/ej2-data';
let searchData: DataManager = new DataManager({
            url: 'https://services.odata.org/V4/Northwind/Northwind.svc/Customers',
            adaptor: new ODataV4Adaptor,
            crossDomain: true
});
let filter: DropDownList = new DropDownList({
    dataSource: searchData,
    query: new Query().select(['ContactName', 'CustomerID']).take(7),
    // map the appropriate column
    fields: { text: 'ContactName', value: 'CustomerID' },
    // set placeholder to DropDownList input element
    placeholder:"Select a name",
    // set true to allowFiltering for enable filtering supports
    allowFiltering: true,
    //set the height of the popup element
    popupHeight: "250px",
    //sort the resulted items
    sortOrder: 'Ascending',
    //bind the filtering event handler
    filtering: (e: FilteringEventArgs) => {
        // load overall data when search key empty.
        if(e.text == '') e.updateData(searchData);
        else{
          let query: Query = new Query().select(['ContactName', 'CustomerID']);
          // change the type of filtering
          query = (e.text !== '') ? query.where('ContactName', 'endswith', e.text, true) : query;
          e.updateData(searchData, query);
        }
    }
});
filter.appendTo('#ddlelement');
<!DOCTYPE html>
<html lang="en">

<head>
    <title>Essential JS 2 DropDownList</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="//cdn.syncfusion.com/ej2/ej2-base/styles/material.css" rel="stylesheet" />
    <link href="//cdn.syncfusion.com/ej2/ej2-inputs/styles/material.css" rel="stylesheet" />
    <link href="//cdn.syncfusion.com/ej2/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>
</head>

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

</html>

Case sensitive filtering

Data items can be filtered either with or without case sensitivity using the DataManager. This can be done by passing the fourth optional parameter of the where clause.

The following example shows how to perform case-sensitive filter.

Source
Preview
app.ts
index.html
import { DropDownList, FilteringEventArgs } from '@syncfusion/ej2-dropdowns';
import { Query, DataManager, ODataV4Adaptor } from '@syncfusion/ej2-data';
let searchData: DataManager = new DataManager({
            url: 'https://services.odata.org/V4/Northwind/Northwind.svc/Customers',
            adaptor: new ODataV4Adaptor,
            crossDomain: true
});
let filter: DropDownList = new DropDownList({
    dataSource: searchData,
    query: new Query().select(['ContactName', 'CustomerID']).take(7),
    // map the appropriate column
    fields: { text: 'ContactName', value: 'CustomerID' },
    // set placeholder to DropDownList input element
    placeholder:"Select a name",
    // set true to allowFiltering for enable filtering supports
    allowFiltering: true,
    //set the height of the popup element
    popupHeight: "250px",
    //sort the resulted items
    sortOrder: 'Ascending',
    //bind the filtering event handler
    filtering: (e: FilteringEventArgs) => {
        // load overall data when search key empty.
        if(e.text == '') e.updateData(searchData);
        else{
          let query: Query = new Query().select(['ContactName', 'CustomerID']);
           //enable the case sensitive filtering by passing false to 4th parameter.
          query = (e.text !== '') ? query.where('ContactName', 'startswith', e.text, false) : query;
          e.updateData(searchData, query);
        }
    }
});
filter.appendTo('#ddlelement');
<!DOCTYPE html>
<html lang="en">

<head>
    <title>Essential JS 2 DropDownList</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="//cdn.syncfusion.com/ej2/ej2-base/styles/material.css" rel="stylesheet" />
    <link href="//cdn.syncfusion.com/ej2/ej2-inputs/styles/material.css" rel="stylesheet" />
    <link href="//cdn.syncfusion.com/ej2/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>
</head>

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

</html>

Diacritics Filtering

The DropDownList supports diacritics filtering which will ignore the diacritics and makes it easier to filter the results in international characters lists when the ignoreAccent is enabled.

In the following sample,data with diacritics are bound as dataSource for DropDownList.

Source
Preview
app.ts
index.html
import { DropDownList } from '@syncfusion/ej2-dropdowns';
  // create local data
let data: string[] = [
        'Aeróbics',
        'Aeróbics en Agua',
        'Aerografía',
        'Aeromodelaje',
        'Águilas',
        'Ajedrez',
        'Ala Delta',
        'Álbumes de Música',
        'Alusivos',
        'Análisis de Escritura a Mano'];
    // initialize DropDownList component
let ddlObj: DropDownList = new DropDownList({
        //set the local data to dataSource property
        dataSource: data,
        // set the placeholder to DropDownList input element
        placeholder: 'Select a value',
        // enabled the ignoreAccent property for ignore the diacritics
        ignoreAccent: true,
        // set true for enable the filtering support.
        allowFiltering: true,
        filterBarPlaceholder: 'e.g: aero'
  });
ddlObj.appendTo('#ddlelement');
<!DOCTYPE html>
<html lang="en">

<head>
    <title>Essential JS 2 DropDownList</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="//cdn.syncfusion.com/ej2/ej2-base/styles/material.css" rel="stylesheet" />
    <link href="//cdn.syncfusion.com/ej2/ej2-inputs/styles/material.css" rel="stylesheet" />
    <link href="//cdn.syncfusion.com/ej2/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>
</head>

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

</html>

See Also