Question

Often I see javascript code where event handlers (like onmousemove) are assigned dynamically.
Example:

document.getElementById('foo').onmousemove = function(e)
{ /* do some stuff with event e */ }

Apparently this ‘e’ parameter is some kind of event object. Where does that come from, as in: who or what defines what this ‘e’ parameter is when the function is called, and can I also do this in static html?
I mean like this:

<div id='foo' onmousemove='Bla(e)'> ... </div>

What should I fill in for ‘e’ to get that same event thing? And can I also combine that with more parameters, like

<div id='foo' onmousemove='Bla(this,e,4)'> ... </div>

where e is, again, supposed to be the event object?

Answer 1

The event object is stored in window.event inside of any event handler, so you do not need to worry about your handler conforming to accepting it as a parameter.

In your second and third examples, the e parameter will be passed as undefined because no variable e exists in that scope (unless you have a global e).