Finding whether a number is triangular number in JavaScript

Triangular Number

Triangular number is the number of points that can fill an equilateral triangle.

For instance − 9 is a triangular number which makes an equilateral triangle with each side of 4 units.

Problem

We are required to write a JavaScript function that takes in a number and returns true if its a triangular number, false otherwise.

Example

Following is the code −

 Live Demo

const num = 9;
const isTriangular = (num = 1) => {
   let i = 4;
   if(num === 1){
      return true;
   };
   if(num === 3){
      return true;
   };
   while(((3 * 1) - 3) <= num){
      if((3 * i) - 3 === num){
         return true;
      };
      i++;
   }
   return false;
};
console.log(isTriangular(num));

Output

Following is the console output −

true