如何在javascript中连接两个数组？ [英] how can I concatenate two arrays in javascript?

问题描述

我看到了回复用另一个
扩展一个数组，所以我尝试了：

I saw this response for extending one array with another so I tried:

console.log(['a', 'b'].push.apply(['c', 'd']));

但它会打印：

2

不应该打印：

['a', 'b', 'c', 'd']

如果不是我做错了什么？

if not what was i doing wrong?

推荐答案

如果不是我做错了什么？

if not what was i doing wrong?

首先， .push 返回数组的新长度：

var arr = [1, 1, 1];
console.log(arr.push(1)); // 4
console.log(arr); // [1, 1, 1, 1]

其次， .apply 需要两个参数：要将函数应用于的对象，以及参数数组。您只传递一个参数，因此您的代码基本上等同于：

Second, .apply needs two arguments: The object you want to apply the function to, and an array of arguments. You only pass a single argument, so your code is basically equivalent to:

['c', 'd'].push()

即你没有在 ['c'，'d'] 数组中添加任何内容。这也解释了为什么你在输出中看到 2 ： ['c'，'d'] 的长度 2 和 .push（）不会向其添加任何元素，因此它的长度仍为 2 。

I.e. you are not adding anything to the ['c', 'd'] array. That also explains why you see 2 in the output: ['c', 'd'] has length 2 and .push() doesn't add any elements to it so it still has length 2.

如果您想使用 .push 来改变原始数组（而不是创建一个新的，如 .concat 确实如此），它必须如下所示：

If you want to use .push to mutate the original array (instead of creating a new one like .concat does), it would have to look like:

var arr = ['a', 'b'];
arr.push.apply(arr, ['c', 'd']); // equivalent to Array.prototype.push.apply(arr, [...])
//              ^   ^--------^
//    apply to arr   arguments
console.log(arr); // ['a', 'b', 'c', 'd']

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参见

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See also

• 如何将某些内容附加到数组中？


• Javascript推送数组值进入另一个阵列

• How to append something to an array?
• Javascript push array values into another array

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