<script>
    /*
    * 手写apply方法   
    * */
    Function.prototype.myApply = function (context, args) {
      console.log(this, 'sss')//fn
      const key = Symbol()
      context[key] = this
      context[key](...args)
      delete context[key]
      return context[key]
    }
    const obj = {
      name: 'zs',
      age: 18
    }
    function fn (a, b) {
      console.log(this)
      console.log(a + b, 'aaa')
      return a + b
    }
    const res = fn.myApply(obj, [1, 2])
    console.log('返回值为', res);
  </script>