Handle the Value Change Event

By default, the value of the SelectBox is changed when the change event is raised. If you need the value to be changed on another event, set the valueChangeEvent option.

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

$(function() {
    $("#selectBoxContainer").dxSelectBox({
        dataSource: selectBoxData,
        valueExpr: 'id',
        displayExpr: 'country',
        valueChangeEvent: 'keyup'
    });
});
Angular
HTML
TypeScript
<dx-select-box
    [dataSource]="selectBoxData"
    valueExpr="id"
    displayExpr="country"
    valueChangeEvent="keyup">
</dx-select-box>
import { DxSelectBoxModule } from "devextreme-angular";
// ...
export class AppComponent {
    selectBoxData = [
        { id: 1, country: "Afghanistan" },
        { id: 2, country: "Albania" },
        // ...
    ];
}
@NgModule({
     imports: [
         // ...
         DxSelectBoxModule
     ],
     // ...
 })
Vue
App.vue
<template> 
    <DxSelectBox ...
        :data-source="selectBoxData"
        display-expr="country"
        value-expr="id"
        value-change-event="keyup"
    />
</template>

<script>
import 'devextreme/dist/css/dx.common.css';
import 'devextreme/dist/css/dx.light.css';

import { DxSelectBox } from 'devextreme-vue/select-box';

export default {
    components: {
        DxSelectBox
    },
    data() {
        const selectBoxData = [
            { id: 1, country: "Afghanistan" },
            { id: 2, country: "Albania" },
            // ...
        ];
        return {
            selectBoxData
        }
    }
}
</script>
React
App.js
import React from 'react';
import 'devextreme/dist/css/dx.common.css';
import 'devextreme/dist/css/dx.light.css';

import SelectBox from 'devextreme-react/select-box';

const selectBoxData = [
    { id: 1, country: "Afghanistan" },
    { id: 2, country: "Albania" },
    // ...
];

class App extends React.Component {
    render() {
        return (
            <SelectBox ...
                dataSource={selectBoxData} 
                displayExpr="country"
                valueExpr="id"
                valueChangeEvent="keyup"
            />
        );
    }
}
export default App;

To process a new SelectBox 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() {
    $("#selectBoxContainer").dxSelectBox({
        onValueChanged: function (e) {
            var previousValue = e.previousValue;
            var newValue = e.value;
            // Event handling commands go here
        }
    });
});
Angular
HTML
TypeScript
<dx-select-box ...
    (onValueChanged)="onValueChanged($event)">
</dx-select-box>
import { DxSelectBoxModule } from "devextreme-angular";
// ...
export class AppComponent {
    onValueChanged (e) {
        const previousValue = e.previousValue;
        const newValue = e.value;
        // Event handling commands go here
    }
}
@NgModule({
     imports: [
         // ...
         DxSelectBoxModule
     ],
     // ...
 })
Vue
App.vue
<template> 
    <DxSelectBox ...
        @value-changed="valueChanged"
    />
</template>

<script>
import 'devextreme/dist/css/dx.common.css';
import 'devextreme/dist/css/dx.light.css';

import { DxSelectBox } from 'devextreme-vue/select-box';

export default {
    components: {
        DxSelectBox
    },
    methods: {
        valueChanged(e) {
            const previousValue = e.previousValue;
            const newValue = e.value;
            // Event handling commands go here
        }
    }
}
</script>
React
App.js
import React from 'react';
import 'devextreme/dist/css/dx.common.css';
import 'devextreme/dist/css/dx.light.css';

import SelectBox from 'devextreme-react/select-box';

class App extends React.Component {
    constructor(props) {
        super(props);
        this.valueChanged = this.valueChanged.bind(this);
    }
    valueChanged(e) {
        const previousValue = e.previousValue;
        const newValue = e.value;
        // Event handling commands go here
    }
    render() {
        return (
            <SelectBox ...
                onValueChanged={this.valueChanged}
            />
        );
    }
}
export default App;

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
};

$("#selectBoxContainer").dxSelectBox("instance")
    .on("valueChanged", valueChangedHandler1)
    .on("valueChanged", valueChangedHandler2);
See Also