Question

I realized that on a webpage, when a form’s UI (checkbox, dropdown list, etc) is changed programmatically, the event handler (onchanged) is not fired? Is this a standard rule — that when a control is changed programmatically, the event handler will never get triggered? Is there any exception?

Answer 1

That is correct, unless as Pointy “pointed” out, you are also firing the event. In jQuery this is as easy as adding a call to .change() in your code that is changing the form.

Ex. –

Html:

<form id="aForm">
    <input></input><br />
    <input></input><br />
    <input type="checkbox"></input><br />
    <input type="checkbox"></input><br />
</form>

jQuery:

$('#aForm').change(function() {
   alert('Your form hath changed!');
})
$('#aForm').hide(function(){
   $(this).change();
});

jsFiddle working example – http://jsfiddle.net/qGLc2/