javascript trigger select change event code example

Example 1: select option trigger in js

/*html*/
<select id="sel" onchange='alert("changed")'>
  <option value='1'>One</option>
  <option value='2'>Two</option>
  <option value='3' selected>Three</option>
</select>

/*Function js*/
var select = document.querySelector('#sel'),
    input = document.querySelector('input[type="button"]');
select.addEventListener('change',function(){
    alert('Yare yare daze');
});

/*RESULT*/
/*When change value trigger alert('Yare yare daze') */

Example 2: javascript trigger change event

There's a couple of ways you can do this. If the onchange listener is a function set via the element.onchange property and you're not bothered about the event object or bubbling/propagation, the easiest method is to just call that function:

element.onchange();
If you need it to simulate the real event in full, or if you set the event via the html attribute or addEventListener/attachEvent, you need to do a bit of feature detection to correctly fire the event:

if ("createEvent" in document) {
    var evt = document.createEvent("HTMLEvents");
    evt.initEvent("change", false, true);
    element.dispatchEvent(evt);
}
else
    element.fireEvent("onchange");