/**
 * Convert a date string like 2011-11-11 to date object in js.
 * 
 * @param  string $date 
 * @access public
 * @return date
 */
function convertStringToDate(dateString)
{
    dateString = dateString.split('-');
    dateString = dateString[1] + '/' + dateString[2] + '/' + dateString[0];
    
    return Date.parse(dateString);
}

/**
 * Compute the end date for productplan.
 * 
 * @param  int    $delta 
 * @access public
 * @return void
 */
function computeEndDate(delta)
{
    beginDate = $('#begin').val();
    if(!beginDate) return;

    endDate = convertStringToDate(beginDate).addDays(parseInt(delta)).toString('yyyy-MM-dd');
    $('#end').val(endDate);
}