Sum of All Numbers in the Nth Row of an Increasing Triangle using JavaScript

Increasing Triangle

For the purpose of this problem, suppose an increasing triangle to be like this −

   1
  2 3
 4 5 6
7 8 9 10

Problem

We are required to write a JavaScript function that takes in a number n and returns the sum of numbers present in the nth row of increasing triangle.

Example

Following is the code −

 Live Demo

const num = 15;
const rowSum = (num = 1) => {
   const arr = [];
   const fillarray = () => {
      let num = 0;
      for(let i = 1; i <= 10000; i++){
         const tempArr = [];
         for(let j = 0; j < i; j++){
            num++;
            tempArr.push(num)
         };
         arr.push(tempArr);
      };
   };
   fillarray()
   return arr[num-1].reduce((a, b)=>a + b, 0);
};
console.log(rowSum(num));

Output

1695