function Contructor(name){
  this.name = name
}

  setTimeout(function(){}.bind(this),1000)

const ctx = {
  a:1,
  test(){
    console.log(this.a);
  }
};
ctx.test();

var b = {
    a: function() {
        console.log(this);
    }
}
b.a();
// this is b

b.a.call(this); // this is window

function B() { 
    this.a = function() {console.log(this.b)}, 
    this.b = 1
}
let b = new B();
b.a();
// this is b object;

    var a = 1;
    this.a;

function Anmai(params) {
  this.params = params
}

let maxNum = Math.max.call(this,5,45,120,-1)
let minNum = Math.min.call(this,5,45,120,-1)
console.log(maxNum ,minNum);

const nums = [5,45,120,-1]
let maxNum = Math.max.apply(this,nums)
let minNum = Math.min.apply(this,nums)
console.log(maxNum ,minNum);

this.x = 9;    // 在浏览器中，this 指向全局的 "window" 对象
var Module = {
  x: 81,
  getX: function() { return this.x; }
};

console.log(Module.getX());// 81

var retrieveX = Module.getX;
console.log(retrieveX());
// 返回 9 - 因为函数是在全局作用域中调用的

// 创建一个新函数，把 'this' 绑定到 module 对象
// 新手可能会将全局变量 x 与 module 的属性 x 混淆
var boundGetX = retrieveX.bind(Module);
console.log(boundGetX()) // 81

btn.onclick(function() {
 console.log(this.className)
});