js代码获取每年每月多少天数，简单易用

// 每月多少天
const getDaysInMonth = (year, month) => {
    let date = new Date(year, month, 1);
    return new Date(date.getTime() - 864e5).getDate();
}
var dateTime=new Date();
var daysInMonth=getDaysInMonth(dateTime.getFullYear(),dateTime.getMonth()+1)