简要谈谈javascriptbind方法

<div id="test"></div>
<script>
    var getDom = document.getElementById;
    console.log(getDom("test"))
</script>

<div id="test"></div>
<script>
var getDom = (function(func){
    return function(){
        return func.apply(document , arguments);
    }
})(document.getElementById);
console.log(getDom("test"))
</script>

var person1 = {
    name : "sky" ,
    getName : function(){
        return this.name;
    }
}
var person2 = {name : "moon"};
var getName = person1.getName.bind(person2);        //绑定person2作为getName函数执行的this
console.log(getName());            //打印的值为moon

var self = {name : "sky" , age: 26}
var getDescription = function(country , city){
    console.log("my name is " + this.name + " , my age is " + this.age + " , I'am from " + country + " " + city);
}.bind(self , "China");
getDescription("WuHan");            //my name is sky , my age is 26 , I'am from China WuHan

<div id="test1">test1</div>
<div id="test2">test2</div>
<script>
    //旧写法，使用_this保存
    var tool1 = {
        name: "sky1",
        bindEvent: function() {
            var _this = this;
            document.getElementById("test1").addEventListener("click", function() {
                console.log(_this.name)
            }, false)
        }
    }
    //新写法，使用bind绑定
    var tool2 = {
        name: "sky2",
        bindEvent: function() {
            document.getElementById("test2").addEventListener("click", function() {
                console.log(this.name)
            }.bind(this), false)
        }
    }
    tool1.bindEvent();
    tool2.bindEvent();
</script>

Function.prototype.skyBind = function(context){
    var func = this;        //就是它！！！这个func就是需要执行，且要绑定context的函数！！！！！！
    return function(){
        return func.apply(context , arguments);            //绑定且执行
    }
}
var person1 = {
    name : "sky" ,
    getName : function(){
        return this.name;
    }
}
var person2 = {name : "moon"};
var getName = person1.getName.skyBind(person2);      
console.log(getName());            //打印的值为moon    

Function.prototype.skyBind = function(){
    var func = this  ,    //还是它！！！这个func就是需要执行，且要绑定context的函数！！！！！！
        context = [].shift.call(arguments) ,            //此时传入的参数就不单单有this的指向，还是其他的参数，按规定第一个参数就是执行环境，拿到它
        args = [].slice.call(arguments);                //arguments具有数组的属性，毕竟JS是个弱类型的语言,但是它毕竟不是数组，用这个方法就是把arguments转换成数组，不用slice换成splice或者其他的都行
    return function(){
        /* 绑定且执行,执行函数的参数为两个数组的合并
         * 这里需要解释的是args是bind绑定时传入的参数，比如下面demo中的China，而下面的arguments则是实际调用时传入的参数WuHan
         * */
        return func.apply(context , [].concat(args , [].slice.call(arguments) ));            
    }
}
//demo
var self = {name : "sky" , age: 26}
var getDescription = function(country , city){
    console.log("my name is " + this.name + " , my age is " + this.age + " , I'am from " + country + " " + city);
}.skyBind(self , "China");
getDescription("WuHan");            //my name is sky , my age is 26 , I'am from China WuHan