event handling - jQuery - Detect value change on hidden input field

Question

I have a hidden text field whose value gets updated via an AJAX response.

<input type="hidden" value="" name="userid" id="useid" />

When this value changes, I would like to fire an AJAX request. Can anyone advise on how to detect the change?

I have the following code, but do not know how to look for the value:

$('#userid').change( function() {  
    alert('Change!'); 
}) 

Answer 1

So this is way late, but I've discovered an answer, in case it becomes useful to anyone who comes across this thread.

Changes in value to hidden elements don't automatically fire the .change() event. So, wherever it is that you're setting that value, you also have to tell jQuery to trigger it.

function setUserID(myValue) {
     $('#userid').val(myValue)
                 .trigger('change');
}

Once that's the case,

$('#userid').change(function(){
      //fire your ajax call  
})

should work as expected.