var maxPower = function (s) {
  var max = 1
  var currentLength = 1
  var index = 0;
  var arr = s.split('');

  while (index <= arr.length - 1) {
    if (arr[index] === arr[index + 1]) {
      currentLength++
      if (currentLength > max) {
        max = currentLength
      }
    } else {
      currentLength = 1
    }
    index++
  };
  return max
};