Insert an Item Between All Elements in an Array
Similar to string.join(), but for an array.
const interleave = (arr, x) => arr.flatMap((e) => [e, x]).slice(0, -1)Example
const arr = [1, 1, 1]
const binary = interleave(arr, 0)
// [1, 0, 1, 0, 1]Explanation
Objective: given an array, insert item x in between every element. Should not be inserted at the beginning or end.
So, first we need to figure out how to insert between every element, we can use Array.prototype.flatMap(). What is is doing is creating a new array, with an item from arr and adding x onto it.
Then it is flattened and repeated for all the elements. However, it adds an extra x at the end, that's what the slice is for. The -1 can be a little confusing, but it's just going to the end of the array. You can read more about that here: Array.prototype.slice()