javascript-algorithms/src/algorithms/string/hamming-distance/hammingDistance.js

/**
 * @param {string} a
 * @param {string} b
 * @return {number}
 */
export default function hammingDistance(a, b) {
  if (a.length !== b.length) {
    throw new Error('Strings must be of the same length');
  }

  let distance = 0;

  for (let i = 0; i < a.length; i += 1) {
    if (a[i] !== b[i]) {
      distance += 1;
    }
  }

  return distance;
}