js 面试题

/**
     * 1. 从文本中找出单词的首字母并互换大小写（data 为示例数据结构, 实际可能更复杂）
     */
    (function () {
      let data = "this is A string for Testing";
      function findAndReverse(data) {
          let str = data.split(' ');
          for (let i = 0; i < str.length; i++) {
              if (str[i][0] >= 'a' && str[i][0] <= 'z') {
                  str[i] = str[i][0].toUpperCase() + str[i].substring(1, str[i].length);
              } else if (str[i][0] >= 'A' && str[i][0] <= 'Z') {
                  str[i] = str[i][0].toLowerCase() + str[i].substring(1, str[i].length);
              }
          }
          let arr = str.join(' ');
          console.log(arr)
      }
      findAndReverse(data)
  })();