推入预填充数组的数组会设置所有元素 [英] Push on array of prefilled arrays sets all elements

问题描述

我正在努力处理奇怪的 Array.prototype.fill 行为:

I'm struggling with a weird Array.prototype.fill behaviour:

const arr = new Array(5)
   .fill([]);
arr[0].push('element pushed to 0 only');
console.log(arr[1]); // ['element pushed to 0 only']

数组中的所有项目都用此字符串填充.我假设所有 [] 数组都指向同一个数组，但是我不明白为什么，有人可以解释吗?

All of the items inside the array are filled with this string. I assume all of the [] array-s are pointing to the same array, but I don't see why, could anyone explain?

推荐答案

在 fill([])中，参数 [] 在调用填充.

与

const subarray = [];
const arr = new Array(5);
arr.fill(subarray);

与

const subarray = [];
const arr = new Array(5);
for (var i=0; i<arr.length; i++) arr[i] = subarray;

换句话说，您在所有索引处都具有相同的子数组: arr [1] 是 arr [0] .

In other words you have the same sub array at all indices: arr[1] is arr[0].

如果您想拥有不同的子数组，您可以这样做

If you want to have different subarrays, you coul do

const arr = Array.from({length:5}, ()=>[]);

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