Autocomplete not trigger Change event in Firefox

by Bruno G.

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<form name="myform" method="post">
<input type="text" name="a" placeholder="input value"/>
<input id="btnSub" type="submit" value="submit" disabled/>
</form>

JavaScript

var form = document.forms.myform,
    elem = form.elements;

$('input[name="a"]').on('change keyup', function(){
		$('#btnSub').prop('disabled', (elem.a.value == ''));
});