问题描述
我想为数组分配一些属性，但前提是它们是数组索引。否则一些实现可能会将底层结构切换到哈希表，我不希望这样。
I want to assign some properties to an array, but only if they are array indices. Otherwise some implementations might switch the underlying structure to a hash table and I don't want that.
例如，这些是数组索引： 0，1，2， 3，4，4294967294
For example, these are array indices: "0", "1", "2", "3", "4", "4294967294"
但这些不是：abcd，0.1， - 0， - 1，2 ，1e3，4294967295
But these are not: "abcd", "0.1", "-0", "-1", " 2", "1e3", "4294967295"
是有一种简单的方法来测试一个字符串是否是一个数组索引？
Is there an easy way to test if a string is an array index?
推荐答案
在ECMAScript 5中，定义如下：
In ECMAScript 5, Array indices are defined as follows:
（
P >>> 0
ToString（ToUint32（ P ））可以完成通过将空字符串与连接起来。
ToString(ToUint32(P)) can be done by concatenating the empty string with the addition operator.
(P >>> 0) + ''
ToString（ToUint32（ P ））等于 P 可以用。
(P >>> 0) + '' === P
请注意，这也将确保 P 确实是String值的形式。
Note this will also ensure that P really was in the form of a String value.
ToUint32（ P ）不等于2 -1可以用
ToUint32(P) is not equal to 2−1 can be checked with the strict does-not-equal operator
(P >>> 0) !== 4294967295
但是一旦我们知道ToString（ToUint32（ P ））等于 P ，以下之一就足够了：
But once we know ToString(ToUint32(P)) is equal to P, one of the following should be enough:
P !== "4294967295"
P < 4294967295
这篇关于检查属性名称是否为数组索引的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！