SOURCE

x=123
let str = x.toString();
console.log(str)
let newStr =[];
for(let i = 0;i<=str.length-1;i++){
    newStr[i] = str[str.length-1-i]
}
 let str2 = newStr.join('')

console.log(str2)
let str3 = parseInt(str2)
console.log(str3)