CoderByte Challenge. Letter Change.

letterchange.js

function LetterChanges(str) {
    var temp = str.split("");
    var alpha = "abcdefghijklmnopqrstuvwxyz".split("");

    function Change(value) {
        var temp2;
        if (value == "z") {
            return temp2 = "a";
        } else if(value.match(/\W/g) || !isNaN(value)){
            return temp2 = value;
        }else{
            /*Alpha Check*/
            for (i = 0; i <= alpha.length - 1; i++) {
                if (value == alpha[i]) temp2 = alpha[i + 1];
            }
            /*Vowel Check*/
            switch (temp2) {
                case "a":
                    return temp2.toUpperCase();
                    break;
                case "e":
                    return temp2.toUpperCase();
                    break;
                case "i":
                    return temp2.toUpperCase();
                    break;
                case "o":
                    return temp2.toUpperCase();
                    break;
                case "u":
                    return temp2.toUpperCase();
                    break;
                default:
                    return temp2;
                    break;
            }
        }
    }

    var result = temp.map(Change).join("");

    return result;

}

document.write(LetterChanges("hello*3"));