别人写的call的实现（xiuyan)

Function.prototype.myCall = function(context, ...args){
  // 把函数挂到目标对象上
  context.func = this;
  // 执行函数
  context.func(...args);
  // 删除目标对象上的函数
  delete context.func;
}
var showName = function(surname, middlename){
  console.log(this.name+' '+surname+' '+middlename);
}
var me = {
  name:'lizzy'
}
showName.myCall(me, 'young','hh')

自己来实现一个apply

Function.prototype.myApply = function(context, args){
  context.func = this;
  context.func(args);
  delete context.func;
}

自己来实现一个bind

Function.prototype.myBind = function(context){
  const fn = this;
  const args = Array.prototype.slice.call(arguments,1)
  if (context){
    context.fn = fn;
    // 这里是最终调用的地方，会传来第二次参数
    var result = function(...args2){
      context.fn(...[...args, ...args2]);
      delete context.fn;
    }
  } else {
    var result = function(...args){
      fn(...[...args, ...args2]);
    }
  }
  return result;
}

var showName = function(...args){
    console.log(this.name, ...args)
  }

var me = {
  name:'lizzy'
}

var you = {
  name:'zzjwd',
  showName: showName.myBind(me,'name2')
}

you.showName('name3') //lizzy name2 name3