事件监听函数添加与消除

 1 function addEventHandler(target, type, func) {
 2     if (target.addEventListener)
 3         target.addEventListener(type, func, false);
 4     else if (target.attachEvent)
 5         target.attachEvent("on" + type, func);
 6     else target["on" + type] = func;
 7 }
 8 function removeEventHandler(target, type, func) {
 9     if (target.removeEventListener)
10         target.removeEventListener(type, func, false);
11     else if (target.detachEvent)
12         target.detachEvent("on" + type, func);
13     else delete target["on" + type];
14 }

 1 var Button1 = document.getElementById("Button1");
 2 var test1 = function() { alert(1); };
 3 function test2() {alert("2")}
 4 addEventHandler(Button1,"click",test1);
 5 addEventHandler(Button1,"click",test2 );
 6 addEventHandler(Button1,"click", function() { alert("3"); } );
 7 addEventHandler(Button1,"click", function() { alert("4"); } );
 8 removeEventHandler(Button1,"click",test1);
 9 removeEventHandler(Button1,"click",test2);
10 removeEventHandler(Button1,"click",function() { alert("3"); });