The onChange event gets triggered when the selection, the checked state or the contents of an element have changed.

JavaScript

In some cases the onchange event only occurs when the element loses the focus. In the event handler JavaScript code or function get be executed. This can for example be used to validate the data that has been entered by the user by calling a specified JavaScript function.

jQuery

jQuery uses the .change() function which gets called onchange:

<input type="text" name="someinput">

$('input[name="someinput"]').change(function() { });

HTML

HTML supports the inline onchange attribute. Most of the time JavaScript code or a JavaScript function gets executed from the onchange attribute, e.g.:

<input type="text" name="someinput" onchange="dosomething()">

Please not that although this is supported most people will say that it is cleaner to remove all inline JavaScript from the HTML.