/*
1、obj相當(dāng)于window
2、type相當(dāng)于onload
3、fn相當(dāng)于匿名函數(shù)
*/
function addEvent( obj,type,fn ){
var saved = null; // 用戶保存上一個事件
if( typeof obj[ "on" + type ] == "function" ){
saved = obj[ "on" + type ]; // 用戶保存上一個事件
};
// 執(zhí)行事件
 obj[ "on" + type ] = function(){
if( saved ){
saved()
};
fn();
};
};
addEvent( window,"load",function(){
alert( "我是尜尜1" );
});
addEvent( window,"load",function(){
alert( "我是尜尜2" );
});
addEvent( window,"load",function(){
alert( "我是尜尜3" );
});