longestLetter

function getLongestRepeating(input: string) {
  const letters = input.split('');

  let longestLetter = '';
  let longestLength = 0;
  for(let i = 0; i < letters.length; i++) {
    const letter = letters[i];
    let currentLength = 0;
    for(let j = 0; j < letters.length; j++) {
      const innerLetter = letters[j];
      if(innerLetter === letter) {
        currentLength += 1;
      }
      else {
        currentLength = 0;
      }

      if(currentLength > longestLength) {
        longestLetter = letter;
        longestLength = currentLength;
      }
    }
  }

  return longestLength;
}

console.log(getLongestRepeating(''));