克隆数组上的Javascript array.push修改原始数组 [英] Javascript array.push on clone array modify original array

问题描述

我发现了一个非常奇怪的问题(对我来说)

I found a really weird (for me) problem

我有这个全局变量ARRAY

I have this global variable ARRAY

var A = [1,2,3,4]

然后在函数中，我创建了本地变量，并为其分配了先前的全局变量

then inside a function, I made local var and assign previous global var to it

function someFunc() {
     var X = A;
}

然后我制作了另一个本地Var，并为其分配了第一个本地var的值

I then made another local Var and assign it with the first local var's value

var Y = X;

然后我将一个新值推到Y

I then push a new value to Y

Y.push(6);

但是，新值(6)不仅被推到Y，而且被推到2个原始数组(X和A).发生了什么?它不是应该只改变Y吗?

but the, the new value (6) didn't only pushed to Y, but also to the 2 original array (X and A). What happened? Doesn't it supposed to only change Y?

请帮助，谢谢.

这是我的完整代码:

var A = [1,2,3,4];


function someFunc(){
    var X = A;
    var Y = X;
    Y.push(6);
    console.log(A);
    console.log(X);
    console.log(Y);
}

$("#test").click(function(){
    someFunc();
});

如您所见，它是通过单击ID为#test的元素触发的.

as you can see, it is triggered by clicking on element with id #test.

所有三个console.log，甚至认为代表不同的变量，它都返回相同的结果，上面带有6的ARRAY

All three console.log, even thought represent different variable, it return the same result, ARRAY with 6 on it

编辑.是的，对此存在类似的问题，但是即使问题相似且解决方案相同，但最初的理解是有什么不同.在我的问题中，我最初问为什么"，因为我不知道那些变量实际上是引用"到同一数组而不是分配"，所以我不知道是否应该搜索如何分配而不是引用，因为我以为使用 = 意味着分配，对不起

Edit. Yes there is a similar question to this, but even though the problem is similar and the solution is identical, but the initial understanding is what different. In my question, I initially asked "Why", because I am not aware of those variable actually 'refer' to same array instead of 'assigning', so I have no idea if I should search for how to assign instead of refer, since I assumed that using = means assigning, sorry

推荐答案

发生的事情是您没有复制只是引用它的数组.您可以使用 slice 创建它的副本:

What happens is that you do not copy the array you just reference it. You can use the method slice to create a copy of it:

var X = A.slice();

请注意，您只能对原始值使用此方法.如果您需要处理对象如何处理，请选中此复选框在Javascript中克隆对象数组?

Do mind that you can use this approach only with primitive values. Check this if you need to deal with objects How do you clone an Array of Objects in Javascript?

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