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

max-char.ts

function maxChar(str: string): string {
  const map = new Map<string, number>();
  let maxValue;
  let maxCount = 0;

  for (let char of str) {
    const newCount = (map.get(char) || 0) + 1;

    if (newCount > maxCount) {
      maxValue = char;
      maxCount = newCount;
    }

    map.set(char, newCount);
  }

  return maxValue;
}

maxChar("abcccccccd"); // c
maxChar("apple 1231111"); // 1

JS Edition:

function maxChar(str) {
  const chars = {};
  let maxCount= 0;
  let maxChar = "";
  
  for(let char of str){
      chars[char] = chars[char] +1 ||1;
  }
  //this give an object 
  for (let key in chars){
      if (chars[key]  > maxCount) {
     maxCount = chars[key];
    maxChar = key;
      }
  }
  return maxChar;
}