Given a string, return the character that is most commonly used in the string.

Maxchar.js

// Given a string, return the character that is most
// commonly used in the string.
// --- Examples
// maxChar("abcccccccd") === "c"
// maxChar("apple 1231111") === "1"

function maxChar(str) {

  const charMap = {};
  
  for (let char of str) {
    charMap[char] = charMap[char] + 1 || 1;
  };
  
  return Object.keys(charMap).reduce((a,b) => charMap[a] > charMap[b] ? a : b);
  
}