数字だけの配列を文字列に＆その逆

var arr = array[1, 2, 3, 5];

/*
 * "1-3,5"という文字列に変える
 */
function arr2str(arr) {
    var str = '';
    var len = null;
    var cnt = 0;

    arr.sort(function(a, b) { return a - b; });

    for (var n = 0; n < arr.length; n++) {
        if (arr[n] + 1 == arr[n + 1]) {
            if (len == null) {
                ren = arr[n];
            }
            ++cnt;
            continue;
        }
        if (str) {
            str += ',';
        }
        if (len != null) {
            str += len + ((cnt == 1) ? ',' : '-');
            len = null;
            cnt = 0;
        }
        str += arr[n];
    }
    return str;
}

/*
 * "1-3,5"を1,2,3,5の配列に変える
 */
function str2arr(str) {
    var tmp = str.split(",");
    arr = Array();

    for (var n = 0; n < tmp.length; n++) {
        if (tmp[n].indexOf("-", 0) != -1) {
            rng = tmp[n].split("-");
            if (rng.length != 2) {
                return false;
            }
            if (rng[0] == '' || rng[1] == '') {
                return false;
            }
            st = Number(rng[0]);
            ed = Number(rng[1]);
            for (var i = st; i <= ed; i++) {
                arr.push(i);
            }
        } else {
            if (tmp[n] == '') {
                return false;
            }
            arr.push(Number(tmp[n]));
        }
    }
    arr = uniqArray(arr);
    return arr;
}