JSFiddle - React, Tailwind, and code Playground

JavaScript

function Palindrome() {
        var revStr = "";
        var str = prompt("Enter a string or number:")
        var i = str.length;
        for(var j=i; j>=0; j--) {
            revStr = revStr+str.charAt(j);
        }
        if(str == revStr) {
            alert(str+" is a palindrome");
        } else {
            alert(str+" is not a palindrome");
        }
    }
Palindrome()