spacedIndexing.js

/**
Write a function that takes three arguments, 2 arrays (a and b) and 1 integer (c)
then returns one array (d) which is created by inserting all elements in b into a at indexes
which are spaced by the integer value.

Consider all possible corner cases and print out the final array (d).
e.g
a = ["a", "b", "c", "d", "e", "f"]
b = ["1", "2", "3"]
c = 2

d = ["a", "b", "1", "c", "d", "2", "e", "f", "3"]
*/

const a = ['a', 'b' , 'c', 'd', 'e', 'f', 'g', 'h'];
const b = ['1', '2', '3', '4'];
const c = 2;
let d = [];

for (let i = 0; i < b.length; i++) {
  let j = ((i + 1) - 1) * c;

  console.log(a.slice(j, j + c), j, j + c);
  
  /// d = [...d, ...a.slice(j, j + c)] /// spread operator
  d = [].concat(d, (a.slice(j, j + c)));
  d.push(b[i]);
}

console.log(d);