SOURCE

Function.prototype.mybind = function(context = window,...args){
    const fn = this;

    let bindFn = function(...newArgs){
        return fn.apply(this instanceof bindFn ? this : context,args.concat(newArgs)) 
    }
    if(this.prototype){
        bindFn.prototype = Object.create(this.prototype)
    }

    return bindFn
}

Function.prototype.myBind = function(context = window, ...args) {
  // 保存原始函数
  const self = this;

  // 返回一个新函数
  return function joker(...newArgs) {
    // 判断是否为构造函数调用
    if(this instanceof joker){
        console.log(999)
       let empty = function(){}
       empty.prototype = Object.assign(self.prototype,context)

       let j = new empty()
       self.apply(j,args.concat(newArgs))
       return j
    }else{
        console.log(888)
        return self.apply(context, args.concat(newArgs));
    }
  };
};




function test(){
    console.log('Outer bind text:',this.name)
}

const o = {
    name:'Just a mybind Demo'
}

const j = test.myBind(o)

const nj = new j()