1function reverseString(s){
2    return s.split("").reverse().join("");
3}
4reverseString("Hello");//"olleH"

1"this is a test string".split("").reverse().join("");
2//"gnirts tset a si siht"
3
4// Or
5const reverse = str => [...str].reverse().join('');
6
7// Or
8const reverse = str => str.split('').reduce((rev, char)=> `${char}${rev}`, '');
9
10// Or
11const reverse = str => (str === '') ? '' : `${reverse(str.substr(1))}${str.charAt(0)}`;
12
13// Example
14reverse('hello world');     // 'dlrow olleh'

1function reverseString(str) {
2    return str.split("").reverse().join("");
3}
4reverseString("hello");

1var s = userInput[0];
2var rev = [];
3for(let i=0;i<s.length;i++)
4{
5    rev.push(s[s.length-1-i]);
6}
7console.log(rev.join(""));