30秒学会 JavaScript 片段 – Index of all matches

Finds all indexes of val in an array.
If val never occurs, returns an empty array.

• Use Array.prototype.reduce() to loop over elements and store indexes for matching elements.

代码实现

const indexOfAll = (arr, val) =>
  arr.reduce((acc, el, i) => (el === val ? [...acc, i] : acc), []);

indexOfAll([1, 2, 3, 1, 2, 3], 1); // [0, 3]
indexOfAll([1, 2, 3], 4); // []

翻译自：https://www.30secondsofcode.org/js/s/index-of-all-matches