偏移量编号的数组项索引 [英] array item index from an offset number

问题描述

我有以下数组：

var list = ['first', 'second', 'third'];

现在我显然可以通过它们的索引分别访问第一个，第二个和第三个元素0 1和2如果我尝试访问 list [4] ，我会收到错误消息。

Now I can obviously access the first, second and third element by their indexes, respectively 0 1 and 2. If I try to access list[4] I will get an error.

有没有办法，如果我尝试访问数组外部的第n个元素，则计数从头开始？这样 list [4] 会返回第一个？

Is there a way so that, if I try to access the nth element outside of the array, the count starts form the beginning? so that list[4] would return "first"?

请记住该数字也可以更大

Keeping in mind that the number could also be bigger multiple times the length of the array itself.

推荐答案

1. 访问不存在的数组元素不会抛出任何错误，但是返回 undefined

var list = ['first', 'second', 'third'];
console.log(list[3]);
// undefined
console.log(list[4]);
// undefined

当索引较大时环绕数组比长度大，那么您可以使用mod运算符，例如

To wrap around the array, when the index is greater than the length, then you can use the mod operator, like this

console.log(list[3 % list.length]);
// first
console.log(list[4 % list.length]);
// second

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