Dear Log,
Today was given over to JavaScript and vacuuming. When I wasn't vacuuming, I was leisurely reading Higher-Order Perl and writing some more notes on translating it all to JavaScript.
Today's interesting stuff was
mainly yet more cases where the Perl code has push @foo,
bar(...) where bar might (directly or indirectly)
return an empty list, or one item, or several; and, to make things
even more interesting, some of the values returned were arrayrefs, so
that I couldn't just say that I'll array-deref whatever values come
back. It's not a case of the Perl being bad, or the JavaScript being bad;
instead, the trouble is the subtleness of the problems that arise from
the apparently safe translation of push @foo, bar(),
as foo.push(bar()). In a day or two, I'll put it
all up at the usual place.
Then, as I was poking at My RSSs Of Interest, it occurred to me that my XSL tricks do improve things by expressing <lastBuildDate>Mon, 23 May 2005 08:57:22 GMT</lastBuildDate> as "Last feed update: Mon, 23 May 2005 08:57:22 GMT". But, it occurred to me that it's not exactly effortless for people to look at that and say "oh, that just updated", or "that was like ten hours ago"
So I thought how I've already used a bit of JavaScript to moregoodify the data in an RSS feed, and a bit of date-wrangling in JavaScript; so I might as well combine the two past approaches and write some JavaScript to convert "Mon, 23 May 2005 08:57:22 GMT" to a Date object and then to figure out how long ago it was, and then to express that as an approximate time-interval, like "Last feed update: about 9 hours ago".
Then I just got crazy and put some other data off into the title="..." attribute of the wrapper-element around the "ago" phrase, so that mousing over "9 hours ago" shows something like "Sun 22 May 2005 04:58:32 PM ADT (Mon, 23 May 2005 08:58:32 GMT)" (modulo your locale and timezone, etc).
(An example RSS with the feature)
Re:Time zone problem?
TorgoX on 2005-05-24T00:18:06
That's very strange. All the time math is done in your browser, which should ideally know its correct TZ offset. But I'll poke around a bit and see if I'm parsing the date wrong or something. What browser are you using?Re:Time zone problem?
vsergu on 2005-05-24T01:55:03
Firefox on Linux. That was at work. I just tried it at home, also Firefox on Linux, and it's the same.Re:Time zone problem?
vsergu on 2005-05-24T02:39:04
Argh! If the string begins with '0', parseInt() assumes it's octal, and '08' isn't a valid octal number and thus returns 0. Maybe subtracting 0 (as opposed to adding 0, which will just give string concatentaion) is better than using parseInt() when you're converting strings to numbers.Re:Time zone problem?
TorgoX on 2005-05-24T04:40:28
D'oh, and just days after I wrote this!!!It seems that if I pass an explicit ",10" to parseInt(), it doesn't do that crazy octalification thing. There, fixedified!
An interesting twist on eval, Function() creates a function reference out of an array of strings.
And this JS 1.5 syntax, which gives an anonymous closure a temporary name so it can refer to itself.
var f = function fact(x) { if (x <=1) return 1; else return x*fact(x-1); }
Despite appearances, there is no fact(). That was just a name for use during the definition of f.
I have tried to do this in Perl and failed. Someone told me one could do it with a Y combinator.
Re:not in HOP
TorgoX on 2005-05-25T02:21:13
One is tempted to do this:But that doesn't work, because sub is defined outside the scope of $f. So you've got to do this:my $f = sub { ($_[0] <=1) ? 1 : ( $_[0] * $f->($_[0] - 1)) };
print $f->(4);That works!my $f;
$f = sub { ($_[0] <=1) ? 1 : ( $_[0] * $f->($_[0] - 1)) };
print $f->(4);(GC note: now $f and that sub constitute a circular data structure, so you need to do $f='whatever'; (or just undef($f)) to break the circularity.)
Re:not in HOP
brev on 2005-05-25T03:06:55
Huh. Now I wonder why what I was trying didn't work. That seems relatively straightforward, with the slight inconvenience of defining the variable first.
Callee was another weirdness I noticed too. Thanks.And with arguments.callee
TorgoX on 2005-05-25T02:29:20
Also:var f = function (x) { if (x <=1) return 1; else return x * arguments.callee(x-1); };
