added comment

Author: MalihaKabir

HackerRank/2DArray-DS/practice2dArray.js

@@ -1,3 +1,4 @@
+// Without Built In Method:
 // const arrayOfHrGlass = [
 //	[ 1, 1, 1, 0, 0, 0 ],
 //	[ 0, 1, 0, 0, 0, 0 ],
@@ -36,9 +37,10 @@ function maxOfHrGlassSum (arr) {
 }
 
 function largestSum (arr) {
-// initiate sum
-let sum;
+// initiate sum with the minimum possible sum. So, since -9 is the lowest possible element according to given Constraints, then sum is their sum, which is:
+let sum = -63;
 for (let i = 0, n = arr.length; i < n; i++) {
+// just in case...
 if (!sum) {
 sum = arr[i];
 }
@@ -50,5 +52,5 @@ function largestSum (arr) {
 console.log(sum);
 }
 
-largestSum(maxOfHrGlassSum(arrayOfHrGlass));
+largestSum(maxOfHrGlassSum(arrayOfHrGlass)); // ans must be 0 (zero)
 console.log(maxOfHrGlassSum(arrayOfHrGlass));