获取某年的某天是第几周

方法一：

var date1 = new Date();
var date2 = new Date(); 
	date2.setMonth(0);
	date2.setDate(1); //当年第一天
var rq = date1-date2;
var s1 = Math.ceil(rq/(24*60*60*1000));
var s2 = Math.ceil(s1/7);
方法二：
/**
 * 获取是否是闰年
 */
function isLeapYear(year) {
    return (year % 400 == 0) || (year % 4 == 0 && year % 100 != 0);
}
/**
 * 获取第个月的天数
 */
function getMonthDays(year, month) {
    return [31, null, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31][month] || (isLeapYear(year) ? 29 : 28);
}
/**
 * 获取某年的某天是第几周
 */
function getWeekNumber(y, m, d) {
    var now = new Date(y, m - 1, d),
        year = now.getFullYear(),
        month = now.getMonth(),
        days = now.getDate();
    //那一天是那一年中的第多少天
    for (var i = 0; i < month; i++) {
        days += getMonthDays(year, i);
    }
    //那一年第一天是星期几
    var yearFirstDay = new Date(year, 0, 1).getDay() || 7;
    var week = null;
    if(yearFirstDay < 7){
    	yearFirstDay = 7;
    }
    week = Math.ceil(days/7);
    return week;
}