javascript - 无法找到用户输入距下一个生日还有多少天

Question

下面将获取距此人生日还有多少天，如果生日已经过，则会给出您生日之前的天数!

我仍然想知道是否可以计算距离下一个生日还有多少天，这需要从 12 月过去并从 1 月开始继续计算。我似乎无法正确理解。

 //Getting birthday and month form form
 var birthdayMonth = document.getElementById('selMonth').value;
 var birthdayDay = document.getElementById('selDay').value;

//Parsing Birthday and month
birthdayMonth = parseInt(birthdayMonth);
birthdayDay = parseInt(birthdayDay);

    //setting date object
    today = new Date( );          // set today's date
    birthday = new Date( );      // set up the Birthday object
    birthday.setMonth(birthdayMonth);      // set birthday month to December
    birthday.setDate(birthdayDay);         // set birthday date to the 15th

if (today < birthday)
 {  //this gets days until next birthday - 
     diff = Math.abs(birthday.getTime( ) - today.getTime( ));
     diff = Math.floor(diff / (1000 * 60 * 60 * 24));
     alert('There are ' + diff + ' days until your birthday ');
  }
else
{ //This gets days since last birthday - 
    diff = Math.abs(today.getTime( ) - birthday.getTime( ));
    diff = Math.floor(diff / (1000*60*60*24));
    alert('It was ' + diff + ' days since your last birthday');

}

Answer 1

试试这个

var birthdayMonth = document.getElementById('selMonth').value;
var birthdayDay = document.getElementById('selDay').value;

birthdayMonth = parseInt(birthdayMonth);
birthdayDay = parseInt(birthdayDay);

    today = new Date( );          // set today's date
    birthday = new Date( );      // set up the Birthday object
    birthday.setMonth(birthdayMonth-1);      // set birthday month to December
    birthday.setDate(birthdayDay);         // set birthday date to the 15th

if (today < birthday)
 {  
     diff = Math.abs(birthday.getTime( ) - today.getTime( ));
     diff = Math.floor(diff / (1000 * 60 * 60 * 24));
     alert('There are ' + diff + ' days until ' + (birthdayMonth)+ ' ' + birthdayDay);
  }
else
{
    alert("B'day has passed!");
}

And here's the JS Fiddle

希望这有帮助!