1.使用数组的 reverse() 方法

let str = 'hello';
let reversed = str.split('').reverse().join(''); // "olleh"

2.从字符串的尾部开始迭代，并逐个添加字符到新的字符串中

let str = 'hello';
let reversed = '';
for (let i = str.length - 1; i >= 0; i--) {reversed += str[i];
}
console.log(reversed); // "olleh"

3.递归

function reverse(str) {if (str === '') {return '';} else {return reverse(str.substr(1)) + str.charAt(0);}
}let reversed = reverse('hello'); // "olleh"

4.reduce()方法

let str = 'hello';
let reversed = str.split('').reduce((prev, next) => next + prev, ''); // "olleh"