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 use getDate() instead. Which means the name is a lie, becasue the logical thing for getDate() 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.