获取concat以使用类似数组的对象

Question

有些地方我将数组更改为像对象这样的数组:

let arr = ['a','b']
let arrLike = {...arr, length: arr.length}
console.log(arrLike)
> {0: "a", 1: "b", length: 2}

它并不完美,但这允许我通过使用合并来覆盖数组.即:

> let a1 = [1,2,3], b1 = [1,2,3]
> Object.assign(a1, arr)
[ 'a', 'b', 3 ]
> Object.assign(b1, arrLike)
[ 'a', 'b']

这是可取的,但我也想让concat工作,

['z'].concat(arr)
> ["z", "a", "b"] // good
['z'].concat(arrLike)
> ["z", {0: "a", 1: "b" length: 2}] // bad

无论如何要修改arrLikeconcat会起作用吗？

Answer 1

您需要定义Symbol.isConcatSpreadable告诉concat()将其视为类似数组:

arrLike[Symbol.isConcatSpreadable] = true;

例:

let arr = ['a','b'];
let arrLike = {
  ...arr, 
  length: arr.length,
  [Symbol.isConcatSpreadable]: true
};

console.log(['z'].concat(arrLike))