// 手写 call
Function.prototype.mycall = function(context){
  var args = Array.from(arguments)
  var obj = args.slice(0,1)[0]
  var fn = this
  obj.fn = fn
  args = args.slice(1)
  return obj.fn(args)
}

function fn(){
  console.log(this.name)
}

var o = {name : ‘lhx‘}
fn.mycall(o)

手写call 、 apply 、 bind