Function that finds the simplest form of summed 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. Like 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.

We are required to calculate the sum in fraction form (i.e., without converting them to decimals).

And return the sum as an array of two elements representing the resulting fraction.

Therefore, let’s write the code for this function −

Example

The code for this will be −

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));
};
console.log(sumArrayOfFractions(arr));

Output

The output in the console will be −

[ 1731, 140 ]