Calculating and adding the parity bit to a binary using JavaScript

Parity Bit

A parity bit, or check bit, is a bit added to a string of bits to ensure that the total number of 1-bits in the string is even or odd.

Problem

We are required to write a JavaScript function that takes in two parameters, one being the wanted parity (always 'even' or 'odd'), and the other being the binary representation of the number we want to check.

The task of our function is to return an integer (0 or 1), which is the parity bit we need to add to the binary representation so that the parity of the resulting string is as expected.

Example

Following is the code −

const parity = 'even';
const bin = '0101010';
const findParity = (parity, bin) => {
   const arr = bin
   .toString()
   .split("");
   let countOnes = 0;
   let res = 0;
   for (let i = 0; i < arr.length; i++) {
      if (arr[i] == 1) {
         countOnes += 1;
      }
   };
   if (parity == 'even') {
      if (countOnes%2 == 0) {
         res = 0;
      } else {
         res = 1;
      }
   } else {
      if (countOnes%2 !== 0) {
         res = 0;
      } else {
         res = 1;
      }
   };
   return res;
};
console.log(findParity(parity, bin));

Output

1