js函数的四种调用方式以及对应的this指向

1 var c=function(){
2    alert(this==window)
3   }
4   c()//true

var myObj={
  value:2,
  inc:function(num){
   alert(this.value+num);
  }
 }
 myobject.inc(1); //结果3，因为this指向myObj

var myObj={
   name:‘myObject‘,
   value:0,
   increment:function(num){
    this.value += typeof(num) ===‘number‘? num:0;
   },
   toString:function(){
    return ‘[object:‘+this.name+‘{value:‘+this.value+‘}]‘;
   },
  
   getInfo:function(){
      return (function(){
        return this.toString();//内部匿名函数不属于当前对象的函数，因此this指向了全局对象window
      })();
  }
 }
alert(myObj.getInfo());//[object window];

 var myObj={
  name:‘myObject‘,
  value:0,
  increment:function(num)   {
   this.value += typeof(num) ===‘number‘ ? num : 0;
  },
  toString:function()   {
    return ‘[object:‘+this.name+‘{value:‘+this.value+‘}]‘;
  },
  getInfo:function(){
   var This=this;//先把当前的this指向存起来
   return (function(){ 
      return This.toString();
   })();
  }
 }
alert(myObj.getInfo());//[Object:myObject {value:0}]

 var fn = function (status){
  this.status = status;
 }
 fn.prototype.get_status = function(){
   return this.status;
 }
 var test = new fn(‘my status‘);
 alert(test.get_status);//my status,this指向test

function MyObject(name){
   this.name=name ||‘MyObject‘;
   this.value=0;
   this.increment=function(num){
   this.value += typeof(num) === ‘number‘ ? num : 0;
  };
  this.toString=function(){
    return ‘[Object:‘+this.name+‘ {value:‘+this.value+‘}]‘;
  };
   this.target=this;
 }
 function getInfo(){
   return this.toString();
 }
 var myObj=new MyObject();
 alert(getInfo.apply(myObj));//[Object:MyObject {value:0}],this指向myObj
 alert(getInfo.apply(window));//[object Window],this指向window