SOURCE

// 字符串大小写取反 aBc => AbC
const fn = (str) => {
    return str.replace(/[a-zA-Z]/g, (s) => {
        if(/[a-z]/.test(s)){
            return s.toLocaleUpperCase()
        } else {
            return s.toLocaleLowerCase()
        }
    })
}

console.log(fn('aBc'))