Question

if i write this

$(document).ready( function () { 
    alert("bla1");
});


$(document).ready( function () { 
    alert("bla2");
});

All good, two alert occurs, but if code is

window.onload = function () {
    alert("bla1");
}


window.onload = function () {
    alert("bla2");
}

second alert not happened, tell someone please, why 2 or more window.onload is wrong?

Answer 1

You assign something to it. You then assign something else to it and overwrite what is there before.

foo = 1;
foo = 2;
// foo is now "2" it is not "1" and "2"

If you want to assign event handlers non-destructively, use addEventListener. You will need to use compatibility methods to support Old-IE. Such methods are built into jQuery via the on method.