4-5 bind,call,apply

1.bind 改变了函数内部this执行的上文环境

    <script>
        /* 改变函数内部的this关键字的指向 */
        var name ="cheng";
        var obj ={
            name:"li"
        }
        /* bind()改变了函数内部this执行的上文环境 */
        var test = function(){
            console.log(this.name)
        }.bind(obj);
        test()  //li
    </script>

2.call 改变函数this的指向,函数调用的时候执行

    <script>
        /* call改变函数this的指向,函数调用的时候执行 */
        var li ="li";
        var obj = {
            name:"cheng"
        }
        var test = function(){
            console.log(this.name)
        }
        test.call(obj)  //cheng
    </script>
    <script>
        /* call(thisObj,params) */
        function sayName(label){
            console.log(label+":"+this.name)
        }
        var name ="window";
        var cheng = {
            name:"cheng"
        }
        var wang = {
            name:"wang"
        }
        sayName("window")  //window:window
        sayName.call(cheng,"chengchao")   //chengchao:cheng
        sayName.call(wang,"女孩子")   //女孩子：wang
    </script>

3.apply 改变函数this的指向,函数调用的时候执行

    <script>
        function go(name,age){
            console.log(this.name+":"+this.age)
            console.log(name)
            console.log(age)
        }
        var li = {
            name:"李梦瑶",
            age:23
        }
        var zhang  = {
            name:"张三丰",
            age:100
        }
        go.apply(li,["li",24])      //传的是数组
        go.call(zhang,"zhang",111)  //一个一个的传参
    </script>