J2EE社區(qū)

1.高級函數(shù) 
    1.1 作用域安全的構(gòu)造函數(shù)
         >例：function Person(name,age,job){
                    this.name=name;
                    this.age=age;
                    this.job=job;
                }
                var person = new Person("xcp",23,"program er");
               alert(person.name);//xcp
                alert(window.name);//undefined                

                但如果我這樣生成對象呢？
                var person = Person("xcp",23,"programer");
                alert(window.name);/xcp
            
                這是為什么呢？
                問題出現(xiàn)在當沒有使用new操作符來調(diào)用構(gòu)造函數(shù)的情況，由于該this對象是在運行時綁定的，所以直接調(diào)用Person(),this會映射到window上

                解決辦法呢？
                function Person(name,age,job){
                    if(this instanceof Person){
                        this.name=name;
                        this.age = age;
                        this.job = job;
                    }else{
                        return new Person(name,age,job);
                    }
                }

    1.2 函數(shù)綁定
        函數(shù)綁定要創(chuàng)建一個函數(shù)，可以在特定中指定參數(shù)調(diào)用另外一個函數(shù)。該技巧常常和回調(diào)函數(shù)與事件處理程序一起使用，以便在見函數(shù)作為變量傳遞的時候保留代碼執(zhí)行環(huán)境。
        例如：var handler ={
                    message :"Event handled",
                    handleClick:function(event){
                            alert(this.message);
                    }
                }
                var btn = document.getElementById("sub");
                EventUtil.addHandler(btn,"click",bind(handler.handleClick,handler));


2.高級定時器
    2.1 setTimeout clearTimeout
    2.2 setIntelval  clearInterval


3.拖放    
    3.1 常用寫法
        EventUtil.addHander(document,"mousemove",function(event){
            var myDiv = document.getElementById("myDiv");
            myDiv.style.left  = event.clientX+"px";
            myDiv..style.top = event.clientY+"px";
        })