Accessing a MySQL database from Node.JS

It depends what you are doing. If you are implementing some web application I can imagine that this callback style would be very handy.

For example, suppose you have an email application and on the page there's an area with contact information. You could fire off the SQL query to get the contact database and have the callback populate the contact information box on screen when it's ready.

The rest of your program just carries on doing whatever it needs to do: which may be nothing... the entire program can be event driven and waiting for events to happen (like the user clicking somewhere).

This style of programming takes a little getting used to, but you don't need to have some linear piece of code going around checking to see what needs to happen next.

If in the example of contact information you need something else to happen once the box is populated then I imagine you'd fire some event that tells your program what to do.

I'm currently working on porting dojo.Deferreds to node.js. On top of them I am also working on some API sugar that makes it really easy to aggregate the results of multiple deferreds:

    (group)
      ('a', db.query('SELECT A ...'))
      ('b', db.query('SELECT B ...'))
      ('c', db.query('SELECT C ...'))
      .addCallback(function(results) {
        p(results) // {a: ..., b: ..., c: ...}
      });

This will make it very easy to run multiple things in parallel, yet handle all of them in one callback.

Check http://github.com/felixge/node-deferred for more info.

Do not use wait() too much, it will be memory expensive.

As the API docs note, wait() can be problematic: "If any other promises are created and made to wait while the first promise waits, the first promise’s wait will not return until all others return. The benefit of this is a simple implementation and the event loop does not get blocked. Disadvantage is the possibility of situations where the promise stack grows infinitely large because promises keep getting created and keep being told to wait()."

You could get around the lack of naturalness by using something like MethodChain [1] to allow you to write code like this:

    posix.rename("/tmp/hello", "/tmp/world")
    .stat("/tmp/world")
    ._(function() {
        sys.puts("stats: " + JSON.stringify(this));
    });

http://jsclass.jcoglan.com/methodchain.html

Try not to use wait() like this.

There was recently committed writeSync, statSync, etc. that perform POSIX API calls synchronously.

Except the fact that the contrast on the actual content is bad. Darker backgrounds and lighter text has been proven to get read less (60+% more if it is lighter background and darker font). The clouds are cool but the contrast is not.

This type of contrast is good for entertainment (movies, video games etc) not code samples. Even if you have to go with a dark background and light text make sure it is not extreme. A good sample of a dark site that is contrastually(I made that up) readable is : http://www.smashlab.com/ OR add a 'high contrast' button that you can click such as on: http://www.merixstudio.com/

Trust me when you get older than 27 you'll thank me.