JavaScript：使值对的数组形成一组值

问题描述

[1，5，9，21]
$ p







$ [ 9]，[9,21]]

我知道我可以 forEach the数组并收集这些值以创建一个新数组。在 _。lodash 中没有使用 forEach ？

解决方案

您可以映射拼接数组并检查索引。如果它不为零，则取其前置，否则为原始数组的第一个元素。

  var array = [1,5,9,21]，result = array.slice（1）.map（（a，i，aa）=> [i？aa [i-1]：array [ 0]，a]）; console.log（result）;  

.as-console-wrapper {max-height：100％！important; top：0; }

更短的版本，如：

  var array = [1,5,9,21]，result = array.slice（1）.map（（a，i）=> [array [i]，a]）; console .log（result）;  

.as-console-wrapper {最大高度：100％！重要; top：0; }

Is there an elegant, functional way to turn this array:

[ 1, 5, 9, 21 ]

into this

[ [1, 5], [5, 9], [9, 21] ]

I know I could forEach the array and collect the values to create a new array. Is there an elegant way to do that in _.lodash without using a forEach?

解决方案

You could map a spliced array and check the index. If it is not zero, take the predecessor, otherwise the first element of the original array.

var array = [1, 5, 9, 21],
    result = array.slice(1).map((a, i, aa) => [i ? aa[i - 1] : array[0], a]);

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

An even shorter version, as suggested by Bergi:

var array = [1, 5, 9, 21],
    result = array.slice(1).map((a, i) => [array[i], a]);

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

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