Finding sum of a range in an array JavaScript

We are required to write an Array function (functions that lives on Array.prototype object). The function should take in a start index and an end index and it should sum all the elements from start index to end index in the array (including both start and end)

Example

const arr = [1, 2, 3, 4, 5, 6, 7];
const sumRange = function(start = 0, end = 1){
   const res = [];
   if(start > end){
      return res;
   };
   for(let i = start; i <= end; i++){
      res.push(this[i]);
   };
   return res;
};
Array.prototype.sumRange = sumRange;
console.log(arr.sumRange(0, 4));

Output

And the output in the console will be −

[ 1, 2, 3, 4, 5 ]