SOURCE

const a = 'juejin';
console.log(a.split('').reverse().join(''))

function isReverser(str) {
    const len = str.length;
    for (var i = 0; i < len / 2; i ++) {
        if (str[i] !== str[len - i - 1]) {
            return false;
        } 
    }
    return true;
};

isReverser('abba');
console.log(isReverser('abba'));
console.log(isReverser('ssdkkjnnew'));