Javascript implementation code to determine how many days there are in a certain month in a certain year Recommended_time and date

The general approach is to first determine which month it is, and then decide how many days it has (usually using switch). If it is February, you have to determine whether the selected year is a leap year, and then decide whether it has 28 or 29 days. This is a very regular approach and also very logical.

However, if it is to achieve the purpose, there is no need to go to such trouble. The new Date("xxxx/xx/xx") date construction method in JS has a wonderful thing. When you pass in "xxxx/xx/0" (number 0), the date obtained is "xx" The last day of the month before the month (the maximum value of the "xx" month is 69, off topic), if you pass in "1999/13/0", you will get "1998/12/31". And the biggest advantage is that when you pass in "xxxx/3/0", you will get the last day of February of xxxx year. It will automatically determine whether it is a leap year and return 28 or 29. You don't have to judge by yourself. It's so convenient! ! Therefore, if we want to select how many days there are in the selected year and month, we only need to

That’s it, isn’t it very convenient? ? For verification, you can also use this method.
The following is the getDaysInMonth(year, month) method written in JS to get the number of days in a certain year and month:

The following is a simple test code:
]<script> function getDaysInMonth(year,month){ month = parseInt(month,10)+1; var temp = new Date(year+"/"+month+"/0"); return temp.getDate(); } alert(getDaysInMonth("2009","11")); </script>