Angular Lookup - Handle the Value Change Event

By default, the Lookup applies a value immediately after an end user chooses an item from the drop-down menu. To change this behavior and apply the value after a user clicks the "Apply" button, assign 'useButtons' to the applyValueMode property.

HTML
TypeScript
  • <dx-lookup
  • [dataSource]="lookupDataSource"
  • valueExpr="id"
  • displayExpr="country"
  • applyValueMode="useButtons">
  • </dx-lookup>
  • import { DxLookupModule } from "devextreme-angular";
  • // ...
  • export class AppComponent {
  • lookupDataSource = [
  • { id: 1, country: "Afghanistan" },
  • { id: 2, country: "Albania" },
  • // ...
  • ];
  • }
  • @NgModule({
  • imports: [
  • // ...
  • DxLookupModule
  • ],
  • // ...
  • })

To process a new Lookup value, you need to handle the value change event. If the handling function is not going to be changed during the lifetime of the UI component, assign it to the onValueChanged property when you configure the UI component.

HTML
TypeScript
  • <dx-lookup ...
  • (onValueChanged)="onValueChanged($event)">
  • </dx-lookup>
  • import { DxLookupModule } from "devextreme-angular";
  • // ...
  • export class AppComponent {
  • onValueChanged (e) {
  • const previousValue = e.previousValue;
  • const newValue = e.value;
  • // Event handling commands go here
  • }
  • }
  • @NgModule({
  • imports: [
  • // ...
  • DxLookupModule
  • ],
  • // ...
  • })

View Demo

If you are going to change event handlers at runtime, or if you need to attach several handlers to the value change event, subscribe to this event using the on(eventName, eventHandler) method. This approach is more typical of jQuery.

JavaScript
  • const valueChangedHandler1 = function (e) {
  • const previousValue = e.previousValue;
  • const newValue = e.value;
  • // First handler of the "valueChanged" event
  • };
  •  
  • const valueChangedHandler2 = function (e) {
  • const previousValue = e.previousValue;
  • const newValue = e.value;
  • // Second handler of the "valueChanged" event
  • };
  •  
  • $("#lookupContainer").dxLookup("instance")
  • .on("valueChanged", valueChangedHandler1)
  • .on("valueChanged", valueChangedHandler2);
See Also