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Posted by mattc at Dec 13, 06 04:36 PM ... Comments (0)

I was just about to write a regular expression, when suddenly ...

I stumbled on the fact that upon feeding dates formatted as RFC 822 (as commonly found in RSS 2.0) in to a newly instantiated Javascript Date object it just handles it. No ifs or buts, it just works. I didn't expect that.

 var foo = 'Fri, 04 Apr 2003 05:04:39 GMT';
 var bar = new Date( foo );
 var woo = bar.getYear()  // woo holds '2003'

How very helpful. This means I could combine some getElementsByTagName construct with Date to give me an array of feed items by date without too much fuss ...

 var foo = new Array();
 // where 'o' is the response from some xmlHTTP request
 var rss = o.responseXML.getElementsByTagName("item");  
 for ( var j = 0; j < rss.length; j++ ) {
    foo.push( new Date( rss[j].getElementsByTagName("pubDate")[0].textContent ) );
     }

But wait. Simon and Mark point out that RSS has many dates and times.

So I wonder how JavaScript handles these?

 // load each date type in to foo
 var foo = new Array('2003-03-21T16:28:40', '2003-04-03T07:45:57-08:00', 'Fri, 04 Apr 2003 05:04:39 GMT', 'Fri, 28 Mar 2003 05:18:59 -0800', '1049379042.0', '2003-03-21T16:28:40', '2003-01-17T13:03:00+00:00', '2003-03-27T19:41:49-06:00' );
 // iterate foo and write the year to the screen
 for ( var i = 0; i < foo.length; i++ ) {
   var bar = new Date( foo[i] );
   // print output, attempt to call getFullYear
   document.write( foo[i] + " - " + bar.getFullYear() + "\n" );
   }

In Opera 9, almost perfectly ...

 2003-03-21T16:28:40 - 2003
 2003-04-03T07:45:57-08:00 - 2003
 Fri, 04 Apr 2003 05:04:39 GMT - 2003 
 Fri, 28 Mar 2003 05:18:59 -0800 - 2003
 1049379042.0 - NaN  // bah!
 2003-03-21T16:28:40 - 2003
 2003-01-17T13:03:00+00:00 - 2003
 2003-03-27T19:41:49-06:00 - 2003

The only error is the obscure '1049379042.0', which I assume is a reference to the number of seconds passed since midnight 1970. I'm not sure who is using that in their pubDate fields !?

IE 6, Firefox 1.5 & Safari 2.0.4 do much worse, only managing to parse and return valid Date objects from 2 out of the 7 dates.

 2003-03-21T16:28:40 - NaN 
 2003-04-03T07:45:57-08:00 - NaN
 Fri, 04 Apr 2003 05:04:39 GMT - 2003
 Fri, 28 Mar 2003 05:18:59 -0800 - 2003
 1049379042 - NaN
 2003-03-21T16:28:40 - NaN
 2003-01-17T13:03:00+00:00 - NaN
 2003-03-27T19:41:49-06:00 - NaN

So, to recap, Opera's Date object supports ISO 8601 date parsing upon construction, everything else doesn't.

I find the ECMA standard terse at the best of times, it's unclear whether it's meant to be doing this or not.

I also see MochiKit provides extensions for this sort of thing via it's DateTime library.

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