reverseString.js

function reverseString(string) {
    var arr = new Array(string.length),
        middle = Math.ceil(string.length / 2);

    for (var x = 0, y = string.length - 1; x <= middle; x++, y--) {
        arr[x] = string[y];
        arr[y] = string[x];
    }

    return arr.join('');
}