We are required to write a JavaScript function that takes in an array of numbers and returns the cumulative sum of every number present at the index that is a multiple of n from the array.
Let’s write the code for this function −
const arr = [1, 4, 5, 3, 5, 6, 12, 5, 65, 3, 2, 65, 9]; const num = 2; const nthSum = (arr, num) => { let sum = 0; for(let i = 0; i < arr.length; i++){ if(i % num !== 0){ continue; }; sum += arr[i]; }; return sum; }; console.log(nthSum(arr, num));
Output
Following is the output in the console −
99
Above, we added every 2nd element beginning with index 0 i.e.
1+5+5+12+65+2+9 = 99