// 3. Sum all numbers in an array containing nested arrays. // arraySum([1,[2,3],[[4]],5]); // 15 var arraySum = function(array) { var result = 0; if(! Array.isArray(array)) { return array; } else { array.forEach(arr => { result += arraySum(arr); }) } return result; }; console.log(arraySum([1,[2,3],[[4]],5]));