Find the Sum of Fractions in JavaScript

We have an array of arrays like this −

const arr = [[12, 56], [3, 45], [23, 2], [2, 6], [2, 8]];

Note that while the array can have any number of elements, each subarray should strictly contain two numbers.

The two numbers in each subarray represents a fraction. For example, the fraction represented by the first subarray is 12/56, by the second is 3/45 and so on.

We are required to write a JavaScript function that takes in one such array and calculates the sum of fractions represented by all the subarrays. Calculate the sum in fraction form (i.e., without converting them to decimals). Return the sum as an array of two elements representing the resulting fraction.

Example

Following is the code −

const arr = [[12, 56], [3, 45], [23, 2], [2, 6], [2, 8]];
const gcd = (a, b) => {
   let num = 2, res = 1;
   while(num <= Math.min(a, b)){
      if(a % num === 0 && b % num === 0){
         res = num;
      };
      num++;
   };
   return res;
}
const sumFrac = (a, b) => {
   const aDenom = a[1], aNumer = a[0];
   const bDenom = b[1], bNumer = b[0];
   let resDenom = aDenom * bDenom;
   let resNumer = (aDenom*bNumer) + (bDenom*aNumer);
   const greatestDivisor = gcd(resDenom, resNumer);
   return [resNumer/greatestDivisor, resDenom/greatestDivisor];
};
const sumArrayOfFractions = arr => {
   return arr.reduce((acc, val) => sumFrac(acc, val));
};

Output

Following is the output in the console −

[ 1731, 140 ]