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array 空位 empty #72

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Huauauaa opened this issue Mar 9, 2023 · 0 comments

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js

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Huauauaa commented Mar 9, 2023

数组的空位

数组的空位指的是：数组的某一个位置没有任何值。
如：Array构造函数返回的数组是空位。

注意：空位不是undefined,空位是没有任何值empty.
in方法：可以用来于检查某个位置是不是空位，返回布尔值。
注意:forEach,filter,some,every方法都会跳过空位,map方法也会跳过空位，但是也会保留这个值。
join()和toString()会将空位视为undefined,而undefined和null会被处理为空字符串。
在ES6中，明确将空位转为undefined

_{Sent from PPHub}

Huauauaa added the js label

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