Introduction to loading examples using n window onloads at the same time

/*
1. Obj is equivalent to window
2. Type is equivalent to onload
3. Fn is equivalent to anonymous function
*/
function addEvent( obj,type,fn ){
var saved = null; // The user saves the previous event
if( typeof obj[ "on" + type ] == "function" ){
saved = obj[ "on" + type ]; // The user saves the previous event
};
// Execute event
 obj[ "on" + type ] = function(){
if( saved ){
saved()
};
fn();
};
};
addEvent( window,"load",function(){
alert( "I am a group 1");
});
addEvent( window,"load",function(){
alert( "I am a group 2");
});
addEvent( window,"load",function(){
alert( "I am a group 3");
});