How to insert a new element in between all elements of a JS array?

Question

I have an array [a, b, c]. I want to be able to insert a value between each elements of this array like that: [0, a, 0, b, 0, c, 0].

I gues

Answer 1

Straight forward way of inserting only between:

const arr = ['a', 'b', 'c'];

arr.map((v, i) => !i || i === arr.length - 1 ? [v] : [0, v]).flat()