Concat在Javascript中的空数组中 [英] Concat in an empty array in Javascript

问题描述

我正在浏览一些代码，我想知道这是如何有用的

I was browsing through some code and I was wondering how this could be useful

grid.push([].concat(row));

据我所知，它与

grid.push([row]);

为什么'concat'大惊小怪？

Why the 'concat' fuss?

推荐答案

当你需要展平数组并且没有包含其他数组的数组时，你想使用 .concat 。例如，

You want to use .concat when you need to flatten the array and not have an array consisting of other arrays. E.g.

var a = [1,2,3];
var b = [4];

情景1

console.log(b.push(a));
// Result: [4, [1,2,3]]

场景2

console.log(b.concat(a));
// Result: [4,1,2,3]

所以你们两个都是数组数组中的场景。由于 []。concat（）只导致数组，推送 [row] ， []。concat（row）具有相同的结果。

So both of your scenarios in an array of array. Since [].concat() results in an array only, pushing both [row], [].concat(row) has the same result.

但是如果你想要一个扁平数组，你的代码需要稍作改动，你必须 .concat 数组行， grid 而非 .push concat的结果，如方案2

But if you want a flattened array, there is a slight change needed in your code, that you have to .concat the array row with grid and not .push the result of concat to it, as shown in scenario 2

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