new 做了什么

    var a=function(){
      this.che1 = function () { console.log(1) }
      this.che2 = function () { console.log(2) }
      this.che3=function(){console.log(3)}
    }
    var b= new a();
    var c={};

    c.__proto__ = a.prototype;
    a.call(c);

    console.log(b)
    console.log(c)