Sum all numbers in an array containing nested arrays using recursion

Problem statement

Sum all numbers in an array containing nested arrays.

input: [1,[2,3],[[4]],5]
output: 15

var arraySum = function(array) {
   // start here
};

Solution:

var arraySum = function (array) {
  let sum = 0;
  for (let i = 0; i < array.length; i++) {
    if (Array.isArray(array[i])) sum += arraySum(array[i]);
    else sum += array[i];
  }
  return sum;
};