Web Words of Wisdom

In case you are wondering where’s do-until (or loop-until) in Java, you might want to remember that

loop {
…
} until (condition);

tastes just the same as

do {
…
} while (!condition);

Here’s a time waster. Why would JavaScript’s parseInt return 0 when you pass on a string like ‘08′ ? Or 668 for ‘01234′ ?

The reason is that the 1-parameter version tries to do it’s best to figure out what radix you are using for your string. So you can have 0xCAFE for a lovely hex number (that can also wake you in the morning ). Guess what 01234 is ? It’s an octal number because it starts with a zero.

If you want ‘08′ to be 8, you can use the second parameter of parseInt which is the radix for the conversion.

Good luck!

Here’s a copy-paste that boiled me for some minutes today (in collaboration with PEAR’s Mail and Mail_Mime, but it wasn’t their fault):

$something = array(
‘key1′ => ‘abracadabra’,
‘key2′ => “Some longer string, {$somearray['somekey']}”, $scalar,
);

All in all, there was a ghost item at $something’s index 0. Yep, in my case above, $something[0] == $scalar.

So here’s the lesson: if an item shows up at index 0 in a PHP array where you defined key=>value pairs, you probably have a value running loose somewhere in your definition…

If you have a Roku SoundBridge, you’ll probably find Radio Roku interesting. It’s a great product, but however, the “radio roku” is an extremely slow website. Today I have searched for stations playing “electro” music and here’s what I got:

Error SELECT stations.id AS id, stations.name AS name, stations.rating AS rating, if(stations_rank.id is null, 1000000000, stations_rank.id) AS rank FROM stations LEFT JOIN countries ON stations.country = countries.id and countries.languages_id= LEFT JOIN languages ON stations.language = languages.id and languages.languages_id= LEFT JOIN genres ON genre = genres.id and genres.languages_id= LEFT JOIN stations_rank ON stations_rank.stream_id = stations.id WHERE (name like ‘%electro%’ or description like ‘%electro%’ or location like ‘%electro%’ or genres.value like ‘%electro%’ or countries.value like ‘%electro%’ or languages.value like ‘%electro%’) ORDER BY rank ASC

Ok… so that’s why the website is moving soooo slow. Here’s a practical list of “don’t do this” from a single query:

• model logic in data retrieval: if(stations_rank.id is null, 1000000000, stations_rank.id) AS rank. You should avoid this. It’s much better to calculate this as an additional field and not to do an evaluation every single time you retrieve results (especially as this calculated field is probably required in looots of listings, what if you want to change this logic?). Also try to avoid SQL constructs specific to a database engine, in this case IF(cond, a, b). Well, if you’ll live all your life in MySQL you may use some functions, ok…
• order by calculated field: ORDER BY rank. Makes any query cache useless and is not properly indexed by most engines.
• field like ‘%value%’. Never use this on a table larger than 1000 rows that you care about. If on MySQL, try the fulltext indexes available on MyISAM. If not, use a solution for a similar fulltext search.
• condition_on_field1 OR condition_on_field2. Most likely it won’t be indexed.

Ok, so why would we care? Because of scalability. We want those tens of millions of users hit our application and browse those pages and do this and that. And we don’t want a datacenter just to handle their simple queries (which is the other solution for badly written queries).

And of course, we all want to sell. Roku has a couple of very good under-promoted audio players (SoundBridge and SoundBridge Radio are brilliant, probably except for a minor glitch with AAC streams). If I would have seen radioroku.com before the product, I’d think “neeah, that’s too slow”…

ECMAScript 4 (currently implemented in ActionScript, but not directly in web browsers which are still dealing with ECMAScript 3 incompatibilities) has a couple of very neat power-features that will save some lines of code, especially when using the E4x extension (ECMAScript 4 XML).

One of them is the double dot (..) operator. As in

myElement..subNode

This is an array of all “subNode” children below myElement. For a Canvas, myCanvas..Label will be an array of all the Labels in your canvas. Neat, huh?

How about the .@ operator? As in…

myCanvas..Label.@(thisXML.@id == “1234″).text

This will help you select directly the first Label with an attribute of id equal to 1234.