jsはある年のある月を獲得します.ある日は一年の中で何週目ですか?

/**
 *            
 *      
 */
function getWeekNumber(y, m, d) {
    var targetDay = newDate(y, m - 1, d);
    var year = targetDay.getFullYear();
    var month = targetDay.getMonth();
    var days = targetDay.getDate();
    //             
    for (var i = 1; i < m; i++) {
        days += getMonthDays(year, i);
    }
    //          
    var yearFirstDay = newDate(year, 0, 1).getDay();
    //      
    days += yearFirstDay;
    var week = Math.ceil(days / 7);
    return week;
}

/**
 *         
 */
function isLeapYear(year) {
    return (year % 400 == 0) || (year % 4 == 0 && year % 100 != 0);
}
/**
 *         
 */
function getMonthDays(year, month) {
    return [31, (isLeapYear(year) ? 29 : 28), 31, 30, 31, 30, 31, 31, 30, 31, 30, 31][month - 1];
}