# Sum array of rational numbers and returning the result in simplest form in JavaScript

## Problem

We are required to write a JavaScript function that takes in an array of exactly two subarrays with two numbers each.

Both the subarrays represent a rational number in fractional form. Our function should add the rational numbers and return a new array of two numbers representing the simplest form of the added rational number.

## Example

Following is the code −

Live Demo

const arr = [
[1, 2],
[1, 3]
];
const findSum = (arr = []) => {
const hcf = (a, b) => b ? hcf(b, a % b) : a;
if(!arr.length){
return null;
};
const [n, d] = arr.reduce(([a, x], [b, y]) => [a*y + b*x, x*y]);
const g = hcf(n, d);
return g === d ? n / d : [n / g, d / g];
};
console.log(findSum(arr));

## Output

Following is the console output −

[5, 6]