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Recently i was experimenting with array push() method in javascript. I created an array, and pushed the same array using push method.

var a=['hello', 4]

a.push(a)

the result was surprising, when i explored the array items in chrome console, there was infinite array produced. i want to know why this is happening. As the push() method adds the element on last.

I was expecting this result 

['hello, 4, ['hello',4]]

but the result was something else, here is the screenshot of chrome console problem screenshot, infinite inner arrays using push method in JavaScript

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1 回答 1

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当您将对象分配给 Javascript（实际上是在大多数类似语言中）中的变量时，该变量会保存对该对象的所谓“引用”。请注意，JS 中的数组是对象，但字符串和数字等原始值不是。

对象分配是“通过引用”的一个结果是，您对该对象所做的任何更改——即使它对碰巧引用同一对象的另一个变量所做的更改——将在您检查原始变量时“显示”。

所以在这里，你开始

var a=['hello', 4]

然后做

a.push(a)

然后是a点已更改的对象（数组）。现在它的末尾多了一个元素——也就是a我们正在讨论的同一个数组。

所以它递归地展开：

a = ['hello', 4, a]
  = ['hello', 4, ['hello', 4, a]]
  = ['hello', 4, ['hello', 4, ['hello', 4, a]]]
   ...

以此类推，无穷无尽。这不需要无限量的内存，因为数组的第三个元素只是对保存数组的内存位置的引用。

于 2020-01-21T18:41:26.163 回答