multiply-array-values-by-num-2.js

const recursiveMultiplier = (arr, num) {
  if(!arr.length) {
    return arr;
  }
  
  let lastElement = arr.pop();
  recursiveMultiplier(arr, num);
  
  arr.push(lastElement*num);
  return arr;
}

let x = [1, 2, 3], num = 2;
let y = recursiveMultiplier(x,num);
console.log(y);