function reverseString(str) { if (!str || typeof str !== 'string' || str.length < 2) return null; return str.split('').reverse().join(''); } const reverse2 = (str) => str.split('').reverse().join(''); const reverse3 = (str) => [...str].reverse().join(''); console.log(reverse('abcdefg')); console.log(reverse2('abcdefg')); console.log(reverse3('abcdefg'));