Leetcode - 520. Detect Capital

/**
 * @param {string} word
 * @return {boolean}
 */
var detectCapitalUse = function (word) {
  if (word.length === 1) {
    return true;
  }

  const isAllLowerCase = (word) => {
    return word.charCodeAt(0) >= 97 && word.charCodeAt(0) <= 122;
  };
  const isAllUpperCase = (word) => {
    return word.charCodeAt(0) >= 65 && word.charCodeAt(0) <= 90;
  };

  if (isAllLowerCase(word[0])) {
    for (let i = 0; i < word.length; i++) {
      if (!isAllLowerCase(word[i])) {
        return false;
      }
    }
  } else {
    if (isAllLowerCase(word[1])) {
      for (let i = 1; i < word.length; i++) {
        if (!isAllLowerCase(word[i])) {
          return false;
        }
      }
    } else {
      for (let i = 0; i < word.length; i++) {
        if (!isAllUpperCase(word[i])) {
          return false;
        }
      }
    }
  }
  return true;
};

Runtime: 97 ms, faster than 63.01% of JavaScript online submissions for Detect Capital.

Memory Usage: 42.4 MB, less than 38.36% of JavaScript online submissions for Detect Capital.