javascript change event code example

Example 1: js select on change value

document.getElementById('my-select').addEventListener('change', function() {
  console.log('You selected: ', this.value);
});

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");

Example 3: js addeventlistener change select

<input id="test" type="text" value="Sélectionnez-moi !" />
<script>
  var elem = document.getElementById('test');
  elem.addEventListener('select', function() {
    alert('La sélection a changé !');
  }, false);
</script>

Example 4: javascript input value change

function updateInput(ish){
    document.getElementById("fieldname").value = ish;
}