js获取当前日期是本月的第几周

在JavaScript中，你可以使用`Date`对象以及一些内置方法来获取当前日期是本月份的第几周。下面是一个示例函数：

function getWeekOfMonth() {
    var now = new Date();
    var oneDay = 24 * 60 * 60 * 1000; // milliseconds in a day
    var n = now.getDay(); // get the day of week (0 is Sunday)
    var d = now.getDate(); // get the current date

    // If it's the first day of the month, adjust to start of last week
    if (n === 0) {
        n = 7;
    }

    // Add days to go to the beginning of this week
    now.setHours(0, 0, 0, 0);
    now.setDate(d - n + 1); // move back to the start of the week

    // Calculate the week number by counting the number of weeks from the beginning of the year
    var weekNumber = Math.ceil((now - new Date(now.getFullYear(), 0, 1)) / oneDay / 7) + 1;

    return weekNumber;
}

这个函数首先获取当前日期和星期几，然后调整到本周的第一天。接着计算从年初到现在经过了多少完整的星期加一，即可得到当前日期所在的本年内的第几周。