How can I trigger an onchange event manually? [duplicate]

Question

I'm setting a date-time textfield value via a calendar widget. Obviously, the calendar widget does something like this :

document.getElementById('datetimetext').value = date_value; 

What I want is:
On changing value in the date-time textfield I need to reset some other fields in the page. I've added a onchange event listener to the datetimetext field which is not getting triggered, because I guess onchange gets triggered only when the element gets focus & its value is changed on losing focus.

Hence I'm looking for a way to manually trigger this onchange event (which I guess should take care of checking the value difference in the text field).

Any ideas?

Answer 1

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"); 

Answer 2

MDN suggests that there's a much cleaner way of doing this in modern browsers:

// Assuming we're listening for e.g. a 'change' event on `element`  // Create a new 'change' event var event = new Event('change');  // Dispatch it. element.dispatchEvent(event);