An implementation of Moore's Voting Algorithm

MooreVoting.js

export const isMajority = (arr, candidate_index) => {
  const candidate = arr[candidate_index];
  let count = 0;

  const halfSize = arr.length / 2;

  for (let i = 0; i < arr.length; i++) {
    if (candidate === arr[i]) {
      count++;
    }
  }

  if (count > halfSize) {
    return candidate;
  } else {
    return false;
  }
};

export const majorityElement = (arr) => {
  let count = 1;
  let candidate_index = 0;
  for (let i = 1; i < arr.length; i++) {
    if (arr[i] === arr[candidate_index]) {
      count++;
    } else {
      count--;
    }

    if (count === 0) {
      candidate_index = i;
      count = 1;
    }
  }

  return candidate_index;
};

const array = [2, 2, 3, 4];

const index = majorityElement(array);

const result = isMajority(array, index);

console.log(result);