JavaScript Range Function

JavaScript Numeric Range

// something comparable to PHP range method. Supports numbers and letters. 
function range(start, end, step) {
    start || alert('must have 1+ params');
    if (!end) {end = start; start = 0;}
    var step = step || 1;
    var range = [];
    var is_num = !isNaN(start);
    start = !is_num ? start.charCodeAt(0) : start;
    end = !is_num ? end.charCodeAt(0) : end;
    step = !is_num ? Math.max(Math.round(step), 1) : step;
    step = start > end ? step * -1 : step;
    while (start != end + step){
        range.push(is_num ? start : String.fromCharCode(start));
        start += step;
        if ((step < 0 && start < end) || (step > 0 && end < start)) {
            break;
        }
    }
    return range;
};