我怎么能在JavaScript的数组的开头添加新的数组元素？ [英] How can I add new array elements at the beginning of an array in JavaScript?

问题描述

我有一个需要添加元素（我检索使用AJAX及时的基础上）在阵列的顶端。

I have a need to add elements (I retrieve on timely basis using AJAX) at the top of an array.

例如，如果我的数组类似如下：

For example, if my array looks like below:

[23, 45, 12, 67]

和从我的AJAX调用的响应是 34 ，我想更新的数组是这样的：

And the response from my AJAX call is 34, I want the updated array to be like the following:

[34, 23, 45, 12, 67]

目前我打算做这样的：

var newArray = [];
newArray.push(response);

for (int i=0; i < theArray.length; i++) {
    newArray.push(theArray[i]);
}

theArray = newArray;
delete newArray;

有没有什么更好的方法来做到这一点？ JavaScript的是否有任何内置的功能，做到这一点？

Is there any better way to do this? Does JavaScript have any built-in functionality that does this?

我的方法的复杂性是 O（N）键，看到更好的实现这将是非常有趣的。

The complexity of my method is O(n) and it would be really interesting to see better implementations.

推荐答案

使用<一个href=\"https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/unshift\"><$c$c>unshift.这就像<一个href=\"https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/push\"><$c$c>push,除了它添加元素的数组，而不是结束的开始。

Use unshift. It's like push, except it adds elements to the beginning of the array instead of the end.

• 不印字 / 推 - 一个元素添加到开始/结束的阵列


• 移 / 弹出 - 移除并返回的第一个/最后一个元素和数组

• unshift/push - add an element to the beginning/end of an array
• shift/pop - remove and return the first/last element of and array

一个简单的图...

   unshift -> array <- push
   shift   <- array -> pop

和图：

          add  remove  start  end
   push    X                   X
    pop           X            X
unshift    X             X
  shift           X      X

查看 MDN阵列文档。几乎每一个有推动能力，语言/从数组中的流行元素也将有不印字/班的能力（有时也称为 push_front / pop_front ）的元素，你不应该来实现这些自己。

Check out the MDN Array documentation. Virtually every language that has the ability to push/pop elements from an array will also have the ability to unshift/shift (sometimes called push_front/pop_front) elements, you should never have to implement these yourself.

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