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 option.

jQuery
JavaScript
var lookupData = [
    { id: 1, country: "Afghanistan" },
    { id: 2, country: "Albania" },
    // ...
];

$(function() {
    $("#lookupContainer").dxLookup({
        dataSource: lookupData,
        valueExpr: 'id',
        displayExpr: 'country',
        applyValueMode: 'useButtons'
    });
});
Angular
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 widget, assign it to the onValueChanged option when you configure the widget.

jQuery
JavaScript
$(function() {
    $("#lookupContainer").dxLookup({
        onValueChanged: function (e) {
            var previousValue = e.previousValue;
            var newValue = e.value;
            // Event handling commands go here
        }
    });
});
Angular
HTML
TypeScript
<dx-lookup ...
    (onValueChanged)="onValueChanged($event)">
</dx-lookup>
import { DxLookupModule } from 'devextreme-angular';
// ...
export class AppComponent {
    onValueChanged (e) {
        let previousValue = e.previousValue;
        let 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
var valueChangedHandler1 = function (e) {
    var previousValue = e.previousValue;
    var newValue = e.value;
    // First handler of the "valueChanged" event
};

var valueChangedHandler2 = function (e) {
    var previousValue = e.previousValue;
    var newValue = e.value;
    // Second handler of the "valueChanged" event
};

$("#lookupContainer").dxLookup("instance")
    .on('valueChanged', valueChangedHandler1)
    .on('valueChanged', valueChangedHandler2);
See Also