javascript bind()

window.color="red";
 
var o={color:"blue"};
 
//全局函数定义
function sayColor(){ 
    console.log(this.color);
}
 
//bind()方法会创建一个函数的实例，其this值会被绑定到传给bind()函数的值
var objectSayColor=sayColor.bind(o);
objectSayColor(); //blue

var myObj = {
 
    specialFunction: function () {
 
    },
 
    anotherSpecialFunction: function () {
 
    },
 
    getAsyncData: function (cb) {
        cb();
    },
 
    render: function () {
        var that = this;
        this.getAsyncData(function () {
            that.specialFunction();
            that.anotherSpecialFunction();
        });
    }
};
 
myObj.render();
//-----------------------------------------------------
var myObj = {
 
    specialFunction: function () {
 
    },
 
    anotherSpecialFunction: function () {
 
    },
 
    getAsyncData: function (cb) {
        cb();
    },
 
    render: function () {
        this.getAsyncData(function () {
            this.specialFunction();
            this.anotherSpecialFunction();
        }.bind(this));
    }
};
 
myObj.render();
//-----------------------------------------------------
Function.prototype.bind() 内部工作原理：
Function.prototype.bind = function (scope) {
    var fn = this;
    return function () {
        return fn.apply(scope);
    };
}
//-----------------------------------------------------
var foo = {
    x: 3
}
 
var bar = function(){
    console.log(this.x);
}
 
bar(); // undefined
 
var boundFunc = bar.bind(foo);
 
boundFunc(); // 3