Iterables - 可迭代对象

• an object which has a Symbol.iterator
• for..of is available

Array-like - 类数组

• an object which has index/length

Array.from work with this two items and transfer them to a real Array

• can deal with surrogate-pair(special chars:𝒳,😂)

在很多内建方法中，对数组的处理都需要兼容 iterables 和 Array-like