Javascript Makes Me Cry: Turning a Date into a String
Working late last night in Alva I wanted to do something that sounded trivial:
When the page loads, get the current date and time, and if a certain input is empty, put it there like this:
28/05/2013 23:45
So, how hard can that be, right? Well not hard, but...
Getting the current date-time is easy: now = new Date();
So, is there something like strftime in Javascript? Of course not. You can get code from the usual places and
have a untested, perhaps broken, limited version of it. And I am not about to add a strftime implementation to use it once.
Sure, there are a number of Date methods that convert to strings, but none of them lets you specify the output format.
So, let's try to do this The Javascript Way, right?
To get the elements I want to put in the value, I used accessor methods. So, obviously, these should give me what I want for the string, right?
now.getDay(), now.getMonth(), now.getYear(), now.getHour() now.getMinute()
Well, they are, at the date mentioned above, respectively: 2, 4, 113, error, error
Ok, the errors are easy to fix from the docs. It's actually getHours() and getMinutes(), so now we have 2, 4, 113, 23, 45 and of those five things, the last two are what one would expect, at least. Let's go over the other three and see why they are so weird:
-
Date.getDay()returned 2 instead of 28 -
Because
getDay()gives you the week day and not the day of the month. Which is absolutely idiotic. So, you have to usegetDate()instead. Which means the name is a lie, becasue the logical thing forgetDate()to return is the whole date. -
Date.getMonth()returned 4 instead of 5 -
Because
getMonth()returns months in the [0,11] range. Which is beyond idiotic and bordering in evil. Come on, Javascript, people have been referring to may as "5" for nearly two thousand years now! What other language does this? Anyone knows one? -
Date.getYear()returned 113 instead of 2013 -
Because it uses offset-from-1900. Which is amazing, and I had never heard of a language doing in a standard type. Because why? So, use
getFullYear()instead.
Now, armed with the right 5 numbers, let's format it. Does Javascript have the equivalent of sprintf or format ? Of course not. In JavaScript, without 3rd party modules, you create strings by addition, like a caveman. Again, I know I could add a format method to the String prototype and make this work, but I am not adding an implementation of format or sprintf just to use it once!
So, this produces that I want:
now.getDate()+'/'+(now.getMonth()+1)+'/'+now.getFullYear()+' '+now.getHours()+':'+now.getMinutes()
Unless... the day or month are lower than 10, in which case it's missing the left-padding zero. Luckily, for the purpose I was using it, it worked anyway. Because OF COURSE there's no included function to left-pad a string. You have to do it by addition. Or, of course, add a 3rd party function that's out there, in the internet, somewhere.
