Filtering

To enable the filtering functionality, set the filterable property to true.

Note that enabling the filtering functionality prevents the options list popup from closing when the DropDownList wrapper leaves the viewport, as it includes a focused input element for the user to provide his filter query.

Basic Configuration

When the filtering functionality is enabled, the component renders a filter input in the drop-down list. On every character input, the component triggers a filterChange event. The event argument contains the typed string value that you can use to filter the source.

To filter the data after a delay, use a similar implementation. You can toggle the loading property and provide the user with a visual indication of the filtering process.

Copy Codeimport { Component, ViewChild } from '@angular/core';
import { Observable, BehaviorSubject, from } from 'rxjs';
import { delay, switchMap, map, tap } from 'rxjs/operators';

@Component({
  selector: 'my-app',
  template: `
    <kendo-dropdownlist
        #list
        [data]="data"
        [filterable]="true"
        textField="text"
        valueField="value"
    >
    </kendo-dropdownlist>
  `
})
export class AppComponent {
    @ViewChild("list") list;

    public source: Array<{ text: string, value: number }> = [
        { text: "Small", value: 1 },
        { text: "Medium", value: 2 },
        { text: "Large", value: 3 }
    ];

    public data: Array<{ text: string, value: number }>;

    constructor() {
        this.data = this.source.slice();
    }

    ngAfterViewInit() {
      const contains = value => s => s.text.toLowerCase().indexOf(value.toLowerCase()) !== -1;

      this.list.filterChange.asObservable().pipe(
            switchMap(value => from([this.source]).pipe(
                tap(() => this.list.loading = true),
                delay(1000),
                map((data) => data.filter(contains(value)))
            ))
        )
        .subscribe(x => {
            this.data = x;
            this.list.loading = false;
        });
    }
}

Minimum Filter Length

The following example demonstrates how to update the data and open the DropDownList only after typing a minimum number of characters.

Copy Code@Component({
  selector: 'my-app',
  template: `
    <p>Open the DropDownList and type minimum 3 characters, e.g. "sma"</p>
    <kendo-dropdownlist
        [data]="data"
        [filterable]="true"
        [textField]="'text'"
        [valueField]="'value'"
        (filterChange)="handleFilter($event)"
    >
    </kendo-dropdownlist>
  `
})
class AppComponent {
    public source: Array<{ text: string, value: number }> = [
        { text: "Small", value: 1 },
        { text: "Medium", value: 2 },
        { text: "Large", value: 3 }
    ];

    public data: Array<{ text: string, value: number }>;

    constructor() {
        this.data = [];
    }

    handleFilter(value) {
        if (value.length >= 3) {
            this.data = this.source.filter((s) => s.text.toLowerCase().indexOf(value.toLowerCase()) !== -1);
        } else {
            this.data = [];
        }
    }
}

Built-in Directive

When the entire set of data is available on the client, you can use the built-in kendoDropDownFilter directive to filter the data on user input. To configure the kendoDropDownFilter directive, provide a DropDownFilterSettings object to it. DropDownFilterSettings enables you to set the case sensitivity of the performed search through the caseSensitive property and the search logic operator which provides the startsWith and contains options.

The provision of theDropDownFilterSettings configuration object is optional. By default, the kendoDropDownFilter directive performs a case-insensitive search with the startsWith operator.

Copy Codeimport { Component } from '@angular/core';
import { DropDownFilterSettings } from '@progress/kendo-angular-dropdowns';

@Component({
  selector: 'my-app',
  template: `
    <div class="example-config">
        <input id="cs" type="checkbox" [(ngModel)]="filterSettings.caseSensitive">
        <label for="cs">Case-sensitive</label>
        <hr />
        <div>
            <input id="stw" type="radio" name="op" (click)="changeFilterOperator('startsWith')" checked>
            <label for="stw">StartsWith Operator</label>
        </div>
        <div>
            <input id="cnt" type="radio" name="op"(click)="changeFilterOperator('contains')">
            <label for="cnt">Contains Operator</label>
        </div>
    </div>

    <kendo-dropdownlist
        [data]="data"
        [kendoDropDownFilter]="filterSettings"
        [textField]="'text'"
        [valueField]="'value'"
    >
    </kendo-dropdownlist>
  `
})
class AppComponent {
    public data: Array<{ text: string, value: number }> = [
        { text: "Small", value: 1 },
        { text: "Medium", value: 2 },
        { text: "Large", value: 3 }
    ];

    public filterSettings: DropDownFilterSettings = {
        caseSensitive: false,
        operator: 'startsWith'
    };

    public changeFilterOperator(operator: string): void {
        this.filterSettings.operator = operator;
    }
}

Suggested Links

• API Reference of the DropDownList