apply第二个参数不是应该是个数组吗？对象也行吗？

Question

如图

Answer 1

Syntax
fun.apply(thisArg, [argsArray])

Parameters

• thisArg

The value of this provided for the call to fun. Note that this may not be the actual value seen by the method: if the method is a function in non-strict mode code, null and undefined will be replaced with the global object, and primitive values will be boxed.

• argsArray

An array-like object, specifying the arguments with which fun should be called, or null or undefined if no arguments should be provided to the function. Starting with ECMAScript 5 these arguments can be a generic array-like object instead of an array. See below for browser compatibility information.

从es5开始支持array-like的object啦，所有array-like就是有length属性，有index作为key的object啦。
你这个object正巧就有length属性，不过没有键值对，所以遍历出5个undefined