如何在不创建新数组的情况下用另一个数组扩展现有 JavaScript 数组

2022-01-31 00:00:00 arrays concatenation javascript

似乎没有办法用另一个数组扩展现有的 JavaScript 数组，即模拟 Python 的 extend 方法.

There doesn't seem to be a way to extend an existing JavaScript array with another array, i.e. to emulate Python's extend method.

我想实现以下目标:

>>> a = [1, 2] [1, 2] >>> b = [3, 4, 5] [3, 4, 5] >>> SOMETHING HERE >>> a [1, 2, 3, 4, 5]

我知道有一个 a.concat(b) 方法，但它会创建一个新数组，而不是简单地扩展第一个数组.我想要一种在 a 明显大于 b 时有效的算法(即不复制 a 的算法).

I know there's a a.concat(b) method, but it creates a new array instead of simply extending the first one. I'd like an algorithm that works efficiently when a is significantly larger than b (i.e. one that does not copy a).

_{注意:这不是如何将某些内容附加到数组? -- 这里的目标是将一个数组的全部内容添加到另一个数组，并就地"完成，即不复制所有元素扩展数组.}

推荐答案

.push 方法可以接受多个参数.您可以使用 spread operator 传递所有第二个数组的元素作为 .push 的参数:

The .push method can take multiple arguments. You can use the spread operator to pass all the elements of the second array as arguments to .push:

>>> a.push(...b)

如果您的浏览器不支持 ECMAScript 6，您可以使用 .apply 改为:

If your browser does not support ECMAScript 6, you can use .apply instead:

>>> a.push.apply(a, b)

或者，如果您认为它更清楚:

Or perhaps, if you think it's clearer:

>>> Array.prototype.push.apply(a,b)

请注意，如果数组 b 太长(问题从大约 100,000 个元素开始，具体取决于浏览器)，所有这些解决方案都将失败并出现堆栈溢出错误.
如果您不能保证 b 足够短，则应使用另一个答案中描述的标准基于循环的技术.

Please note that all these solutions will fail with a stack overflow error if array b is too long (trouble starts at about 100,000 elements, depending on the browser).
If you cannot guarantee that b is short enough, you should use a standard loop-based technique described in the other answer.

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