使用JavaScript获取指定月份中的天数？

Question

假设我有月份和数字。

Answer 1

// Month here is 1-indexed (January is 1, February is 2, etc). This is

// because we're using 0 as the day so that it returns the last day

// of the last month, so you have to add 1 to the month number 

// so it returns the correct amount of days

function daysInMonth (month, year) {

    return new Date(year, month, 0).getDate();

}

// July

daysInMonth(7,2009); // 31

// February

daysInMonth(2,2009); // 28

daysInMonth(2,2008); // 29

Answer 2

Date.prototype.monthDays= function(){

    var d= new Date(this.getFullYear(), this.getMonth()+1, 0);

    return d.getDate();

}

Answer 3

以下代码获取任何有效的datetime值，并返回关联月份中的天数...消除了其他两个答案的歧义...

 // pass in any date as parameter anyDateInMonth

function daysInMonth(anyDateInMonth) {

    return new Date(anyDateInMonth.getFullYear(), 

                    anyDateInMonth.getMonth()+1, 

                    0).getDate();}