Reverse Words in a String III

LeetCode題目: 557. Reverse Words in a String III

My solution:

/**
 * @param {string} s
 * @return {string}
 */
let reverseWords = s => s.split(' ').map(letter => {
    let reverseLetter = '';
    for(let i=0; i<letter.length; i++) {
        reverseLetter = letter[i] + reverseLetter;
    }
    return reverseLetter;
}).join(' ');