事件绑定 跨浏览器

if(document.addEventListener){
    this.addEvent = function(elem,type,fn){
        elem.addEventListener(type,fn,false);
        return fn;
    };
    
    this.removeEvent = function(elem,type,fn){
        elem.removeEventListener(type,fn,false);
    };
}else if(document.attachEvent){
    this.addEvent = function(elem,type,fn){
        var bound = function(){
            return fn.apply(elem,arguments);
        };
        elem.attachEvent("on" + type,bound);
        return bound;
    };
    
    this.removeEvent = function(elem,type,fn){
        elem.detachEvent("on" + type,fn);
    };
}


//用法

addEvent(window,"load",function(){
    var elems = document.getElementsByTagName("div");
    alert(elems.length);
    for(var i = 0; i < elems.length; i++)(function(elem){
            var handler = addEvent(elem,"click",function(){
                this.style.backgroundColor = this.style.backgroundColor == "" ? "green" : "";
                removeEvent(elem,"click",handler);
            });
        })(elems[i]);
    
});