JavaScript中使用ASCII码进行字符串大小写转换

字符转ASCII码：str='a'; str.charCodeAt()
ASCII码转字符：String.fromCharCode(num)

// 将字符串中的大写转为小写
function toLowerCase(s: string): string {
  let res = "";
  for (let i = 0; i < s.length; i++) {
    let c = s.charCodeAt(i);
    if (c >= 65 && c <= 90) {
      res += String.fromCharCode(c + 32);
    } else {
      res += s[i];
    }
  }

  return res;
}
toLowerCase("azAZ");   //"azaz"