Find the most commonly used character in string

maxChar.js

function maxChar(str) {
  const charMap = {};
  let max = 0;
  let maxChar = '';

  // create character map
  for (let char of str) {
    if (charMap[char]) {
      // increment the character's value if the character existed in the map
      charMap[char]++;
    } else {
      // Otherwise, the value of the character will be increamented by 1
      charMap[char] = 1;
    }
  }

  // find the most commonly used character
  for (let char in charMap) {
    if (charMap[char] > max) {
      max = charMap[char];
      maxChar = char;
    }
  }

  return maxChar;
}