I’ve seen a day I never thought would come:  the day I turned into a hipster!

If you’ve been following this blog, you’ll have noticed that throughout 2011 I’ve been working more and more in Javascript, more specifically with Node.JS.

The last few months have been especially Node.JS-centric. During the day, I’ve been building architectural improvements into Jabbakam. Evenings and weekends, I’ve been  hacking about on the Live Unsigned mobile site. All of my recent projects revolve around Node.JS, and I’ve been loving it. Node is incredibly interesting and powerful, and it is giving my brain a workout.

However, Javascript itself has a few niggly bits that become more problematic the larger the project gets. Issues with structure and maintainability of code motivate projects such as Joose and Backbone.js. One of the things that has been bugging me is having to hack in class-based inheritance. After a lot of experimentation, I settled on Prototypal Inheritance, which does the job to an extent, but left me dissatisfied .

So, the other day I finally broke down and tried CoffeeScript.

When CoffeeScript first came out I resolved never to bother with it. It is clearly for Ruby people who don’t quite understand Javascript. Since then it’s been getting a lot of press, and it now even has its own book!

Anyway, I was up the other night, waiting for my daughter to wake up in screaming pain as razor-sharp pieces of enamel slowly bored through her gums. With nothing better to do, I decided to play around with CoffeeScript.

I was up and running in no time, installing the Node.JS Module and browsing the Little Book of CoffeeScript. After about an hour I had effortlessly written some additions to Live Unsigned which integrated seamlessly. To be honest, I feel like a bit of a muppet for not trying it sooner.

After just a couple of days playing around with it, CoffeeScript has now become a major part of my toolkit. The syntax is elegant, nicely lending itself to clean coding, and code can be reused easily, improving project structure. CoffeeScript compiles to pretty clean Javascript, and from what I can make out, the better you understand Javascript, the better CoffeeScript you can write.

So yes, I am now coding in CoffeeScript.

I am now a hipster.

There is nothing left for me but to rush out, buy some skinny jeans and a Macbook Air and learn Vim.

Oh, God.

In this post, we’re going to make that example slightly more complex by introducing dependencies within the modules. Now the code must be able to handle these dependencies for both the client side and the server side.

In the last post, we built a simple module consisting of a single function that returned a greeting:

var Greetings = function() { }
Greetings.prototype.hello = function(who) {
   return "Hello "+who;
}
module.exports = Greetings;

At this point, it would be very useful to sanitize and validate the parameter passed to the “hello” function. We could obviously build this functionality directly into the code, but this is exactly the sort of thing that should be abstracted into its own module(s).

For the purpose of this example, we’ll simply include the functionality to give the parameter passed a “trim”; after some hacking and snippet-borrowing from node-validator by Chris O’Hara, we can build another simple module called Tidy:

var Tidy = {
   whitespace: '\\r\\n\\t\\s',
 
   trim: function(str) {
      var whitespace =  '\\r\\n\\t\\s';
      str = str.replace(new RegExp('^['+this.whitespace+']+|['+this.whitespace+']+$', 'g'), '')
      return str;
   }
}
module.exports = Tidy;

We can now improve our Greetings module, including the dependency and functionality:

var Tidy = require('./tidy');
 
var Greetings = function() { }
Greetings.prototype.hello = function(who) {
   who = Tidy.trim(who);
   return this.hello(who);
}
module.exports = Greetings;

To see if this will work as expected, let’s add some spaces to the parameter passed in the NodeJS script:

var Greetings = require('./greetings');
var greetings = new Greetings();
console.log(greetings.hello('  Node   ')+"!");

When we run it, this is what we see:

$ node runner.js
Hello Node!

Good, so this works on the server side, but let’s test its behaviour on the client side. Again, we should add some spaces to the parameter passed to ensure that it is working:

<script type="text/javascript"> </script>
<script src="greetings.js" type="text/javascript"> </script>
<script type="text/javascript"> </script>

Unfortunately, we now see the following error:

require is not defined
[Break On This Error] var greetings = new Greetings();

Our attempt to “require” the dependency in the Greetings module has broken the client side. To fix this, we need to define our own require() function, much like we had to for the module object. We do this by creating a new front end-only script, which we’ll call “middle-end.js”.

var require = function(module) {
   document.write('<script src="'+module+'.js" type="text/javascript"> </script>');
}
 
var module = {
   exports: undefined
};

(Obviously we should include much more error checking, but this will be enough for our example).

We modify our html as follows:

<script src="middle-end.js" type="text/javascript"> </script>
<script type="text/javascript"> </script>
....

Now when we reload the page in the browser, all should work as expected. Huzzah!

This is just a very simple example of what can be done when JavaScript code is shared between the client and server sides—the “Middle End”. This concept becomes really exciting when you start thinking about potential approaches to form validation, session management, and even display logic. This is definitely something worth playing around with.

All of the code is available as a Gist.

In my previous post, I talked about Kyle Simpson’s concept of a Middle End—a layer between the front end and back end. Today, I’m going to sketch out my very simple experiments with constructing such a layer.

What I am focusing on here is simply a means of sharing JavaScript code between the client side and the server side.

Let’s start with a very simple NodeJS Module, greetings.js:

var Greetings = function() { }
Greetings.prototype.hello = function(who) {
   return "Hello "+who;
}
module.exports = Greetings;

Next, let’s create a very simple NodeJS script that imports this module, and uses it:

var Greetings = require('./greetings');
var greetings = new Greetings();
console.log(greetings.hello('Node')+"!");

When we run it, this is what we get:

$ node test.js
Hello Node!

All very simple stuff.

Now, suppose we want to use the Greetings module in our front end web app. 

<script src="greetings.js" type="text/javascript"> </script>

Well, it runs and we get the desired output. However, Firebug reports an error within the greetings.js file:

module is not defined
[Break On This Error] module.exports = Greetings;

The solution to this issue is to “mock up” the module object so the error isn’t thrown:

var module = {
   exports: undefined
};

Run it again, and now we see no errors.

Great, so it’s working. We can share simple modules between the client and the server sides.

But what if we want to have a more complex module? One that has some dependencies?

That will be discussed in the next post.

All of the code is available as a Gist.

One of the talks was discussing the concept of the Middle End, by Kyle Simpson. This really made an impression on me, and I think I probably bored Kyle in the bar afterwards with my drunken enthusing. When we arrived back home, my aim was to start playing around with the idea of a Middle End as soon as possible. Unfortunately, as is life, events took over (such as discovering one is going to become a dad!) and these thoughts were consigned to the back of my mind.

Until now

The more I hack around with NodeJS the more I’ve been able to experiment with different aspects of it. Well, today I began hacking around with some Middle End concepts.

The idea of the Middle End is quite simple.

In a web application there is traditionally the Front End and the Back End. The front end handles all of the client side processing (such as rendering some whizzy JQuery plugins or whatever). The back end handles the actual hard crunching, such as retrieving and adding data from the storage engine.

However, there are certain aspects that both the front end and the back end need to handle. Some things that spring to mind are: session managment, input validation and possibly some display logic (Kyle’s post goes into some more depth here).

Currently these aspects are handled both by the front end and back end code, but as traditionally front end code is JavaScript where as back end code maybe Ruby, PHP, Python, etc that means there ends up being duplication of code. Two different languages doing the same thing.

This is in direct violation of the DRY principal. Quite simply, this is a waste.

There is a solution to this waste. Using JavaScript on the server side, effectively code can now be reused. But how can you use the same piece of code for the client side as well as the server side? In my next post I’ll be looking at how to do that.

I’ve been researching automated deployment of NodeJS applications, and found this excellent blog post to help me out:

Deploying Node.JS Apps, by Ben Gourley.

Plus this question on stack overflow on nginx proxying should help me out.

That’s it. now I just need some time to play around with this stuff!

Also, if anyone knows of a really simple, easy to organize bookmarking site please let me know!

I have high hopes for the conference. Last year I didn’t even attend the main event, just the pre-party on the Friday night and still came away with a load of ideas! One conversation lead me to completely rewrite major parts of the Jabbakam system. Who knows what new thoughts will spark in my head when I actually go to the real thing?

For updates, follow me on Twitter.

What I have been working on is having a single parent process that runs constantly in the background, and this parent is responsible for child processes which actually do the work. One thing I found particularly interesting was how the parent can handle a child crashing, and also what happens to the children when the parent is killed. Below is the culmination of my hackings, it comprises of two simple scripts, a child script, and a parent. I have committed them to my GitHub account, so feel free to clone, fork, hack or whatever.

Note: Node version at time of writing was v0.4.9 and running off a Debian machine.

Child Worker

For this experiment we need a really simple child script. It doesn’t have to do anything apart from tell us it is alive when it is running, and then kill itself so we can see how the parent handles this event.

The main bulk of this script is the loop:

var child_loop = function() {
   // report the current loop
   console.log("Child loop: "+NUMBER_OF_LOOPS);
 
   // to simulate the child exiting itself without just running
   // out of program, if we have completed the desired number of
   // loops, exit this process
   if( NUMBER_OF_LOOPS < 0 ) {
      console.log("Child finished loop");
      process.exit();
   }
 
   // sleep for a bit, then continue through the loops
   setTimeout(function() { child_loop() }, LOOP_SLEEP_TIME);
   NUMBER_OF_LOOPS--;
}
 
// start the loop
child_loop();

As you can see this loops for NUMBER_OF_LOOPS, outputting what loop it is currently on. At the end of the loop it kills itself, informing us whilst it does it.

So, this is fine whilst the child is running, but we also need to try and get the child to clean up after itself if it is killed by an external process – i.e. the parent. After some playing around and reading of the documentation, I ended up with this:

// detect and report if this child exited
process.on("exit", function() {
   console.log("Child exiting");
});
// detect and report if this child was killed
process.on("SIGTERM", function() {
   console.log("Child SIGTERM detected");
   process.exit();
});

I need to go more in depth, but whilst testing, this seemed to correctly handle the child being terminated externally.

So, that’s the child script. You can run this directly from the command line and it does what is expected. Good, so we’re all ready to build the parent so it can spawn multiple children.

Parent

This was the main focus of the experiment. The chief concerns were:

• Ensuring the process ran indefinitely as a daemon
• Spawning the children
• Handling a child that crashed or exited
• Cleaning up the children when the parent was exited

The first point is relatively simple, all we need is an indefinite loop:

loop = setInterval(function() {
   // functionality here
}, LOOP_SLEEP_TIME);

Handling the children was a little more complex. In the end I created an array that would contain the children. Within the main loop, I then ran through that array, checking to see if the child existed, if not then spawning it. Notice how the loop is returning itself into the variable “loop”. This will be important later.

var spawn = require('child_process').spawn;
var loop = setInterval(function() {
   for(i=0; i

This is fine for creating the children, but then what if a child dies? Simple really. The parent needs to listen for the exit event on the child. When detected, ensure that the array element for that child is cleaned out, and then in the next loop, the child will be respawned.

children[i].on('exit', function (code) {
   children[i] = undefined;
});

Next, what if the parent is killed. We need to make sure we don’t leave any orphaned children behind. After some playing around, I found that two events needed to be listened for. Again, the exit event, this time on parent, but also the SIGTERM event on the parent.

When a SIGTERM event is detected, we simply tell the script to exit cleanly:

process.on("SIGTERM", function() {
   console.log("Parent SIGTERM detected");
   // exit cleanly
   process.exit();
});

Now, when the exit event is triggered, we can clean up the children. One thing we must also do, is stop the Interval of the main loop. If we didn’t do this, when the children were killed, the next “tick” of the loop, then they would all be created again. It’s possible that this could happen before the main script has exited, orphaning the children. We can eaily do this as we have the variable that the setInterval call has been saved into.

process.on("exit", function() {
   // ensure no more "ticks"
   clearInterval(loop);
 
   // kill all children!
   for(i=0; i<TOTAL_CHILDREN; i++) {
      if(children[i] != undefined) {
         console.log("Kill child "+i);
         children[i].kill();
      }
   }
});

That is it for the main bulk of the script. As I’m testing and running it on Debian I am using start-stop-daemon to run the parent as a daemon. As such I’ve had to add the functionality for creating a .pid file. One issue I had with this, and I have no idea why, is when I tried to write the process.pid value to a file it filled the file up with nonsense. However, if I converted it to a string (which from what I can tell it already was) before writing it to the file, then it worked fine.

var pid = ""+process.pid; // need to turn into a string
fs.writeFile('/tmp/parent.pid', pid, function (err) {
   if (err) throw err;
});

You can see the complete parent and child scripts on my Github repository.

Running

Now we have our scripts, we need to run them to see if they actually behave as expected. In Debian (and derivatives) this is pretty simple:

To start

start-stop-daemon --start --exec /home/rob/workspace/NodeJS/process/parent.js --pidfile /tmp/parent.js.pid

And to stop

start-stop-daemon --stop --pidfile /tmp/parent.js.pid

As we are not running the process in the background then you will need to have two terminal windows open. Also, you will be able to see the output which explains what is going on.

You should be able to easily convert the script to log to a file (I recommend Vision Media’s Log.js) and then write an init.d script using the start-stop-daemon functionality to create a background daemon process .

You should be able to see that we now have the ability to run a Node.JS daemon process which can spawn multiple children, ensuring it can keep a consistent number of children available, and then handle the cleanup if that daemon process is killed. This opens up lots of possibilities!

Again, feel free to clone, fork, hack, improve, etc the code for this.

Instantly I ran into problems:

$ ./configure
Traceback (most recent call last):
  File "/Users/greim/nodestuff/node/tools/waf-light", line 157, in
    import Scripting
  File "/Users/greim/nodestuff/node/tools/wafadmin/Scripting.py", line 146
    except Utils.WafError, e:
                         ^
SyntaxError: invalid syntax

I’m trying to install this on my Arch Desktop, which has Python version 3.1.3 installed. After some research I found that it was a compatibility issue between Python 2.x and 3.x.

I didn’t really want to remove Python 3 as I’d had dependency hell recently. Inspired by an answer on StackOverflow, I had a dig about in my /usr/bin directory to see if there was both Python v3 and Python v2 installed. Fortunately there was: /usr/bin/python2

Note: Following a comment by eveningsky below, there is a much easier way to work around the problem.

mkdir /tmp/bin
ln -s /usr/bin/python2 /tmp/bin/python
export PATH=/tmp/bin:$PATH

You can now carry on as normal. I have kept my nasty hack below just in case for some absurd reason the above doesn’t work for you.

Many thanks eveningsky!

Old Version

#!/usr/bin/env python2

WAF=python2 tools/waf-light

Now I have Node JS version 0.4.0 running on my Arch box.

In the first part of this tutorial we looked at reading a document from CouchDB and keeping our markup separate from our code using Haml templates. We arrived at the point where we clicked on a link, but nothing happened. Today we are going to put that right with some very simple routing.

The URL Module

The basis of all routing is the URL. Fortunately, Node has some basic functions which handle reading the URL so we can then decide what the user is actually trying to do.

First, we want to make sure we have included the URL module.

var sys = require('sys'),
fs = require('fs'),
http = require('http'),
url = require('url');

The next step is to extrapolate the path name from the URL that the user has visited:

var url_parts = url.parse(req.url);
sys.puts(url_parts.pathname);

Now, when I go to http://127.0.0.1:8000/create in Chromium, the system output is as follows:
/create
/favicon.ico

As you can see I have to deal with /create but also /favicon.ico – unfortunately I don’t have one. We’ll deal with that later by using a 404 error.

The pages we want to be dealing with are as follows:

• /
• create
• /edit

For simplicity’s sake we’ll put them into a switch statement:

switch(url_parts.pathname) {
case '/':
sys.puts("display root");
break;
case '/create':
sys.puts("display create");
break;
case '/edit':
sys.puts("display edit");
break;
default:
sys.puts("oh dear, 404");
}

If you test this out you should see the relevant text displayed in the standard output.

Tidy up Existing Code

Now we have a basic router telling us that it has detected which page the user wants to display, but is then displaying the default page regardless. To correct this we need to put our existing code within a function and then call that function in the relevant part of the switch statement.

So, create a new (sub) function called display_root() in the main bulk of the http.createServer() function, expecting a url, a server request object and aserver response object as parameters:

function display_root(url, req, res) {
...
}

Within the body of the function, you want to insert the main bulk of the application that we wrote last time. I have included the complete code at the bottom of this tutorial, and all code is of course on GitHub.

Now call this function within the switch statement:

display_root(url_parts.pathname, req, res);

Handling Missing Pages

As said, Chromium is looking for a favicon.ico file, but currently this application doesn’t have one. As such it needs to be able to handle missing files gracefully, with the correct 404 response.

Create a new function within the main bulk of the http.createServer() function:

function display_404(url, req, res) {
res.writeHead(404, {'Content-Type': 'text/html'});
res.write("<h1>404 Not Found</h1>");
res.end("The page you were looking for: "+url+" can not be found");
}

Notice that we have specified the header to be 404.

Now you can call this from within the switch:

display_404(url_parts.pathname, req, res);

You can test it out by going to http://127.0.0.1:8000/qwerty
You should see:

404 Not Found
The page you were looking for: /qwerty can not be found

We could use a Haml template to move the content out of the code, but for the purposes of this tutorial it will suffice.

The Form

Now we want to generate a “Create” page – which will be a form allowing us to enter a list name and 1-5 items. (Note: I have changed from 10 items to 5 for no other reason that I am lazy, and don’t particularly want 10 things on my list, also it keeps the code a bit more clean!)

First, create the Haml template that will be used. We’ll keep this very simple for now. The key part is the form generation. After some trial and error, this mark-up seemed to work:

%form(action=url method="post")
      :each i in [0,1,2,3,4]
        %p %label Item
           %input(type="text" name="item[]")
      %p
        %input(type="submit" value="Create List")

You may want to read up on Haml here: http://haml-lang.com

The function for displaying the page is as follows:

    function display_create(url, req, res) {
	res.writeHead(200, {'Content-Type': 'text/html'});
	fs.readFile('./templates/create.haml', function(e, c) {
	    var data = {
		title: "Create New List",
		message: "Please enter up to 5 things to remember",
		url: url
	    };
	    var html = haml.render(c.toString(), {locals: data});
	    res.end(html);
	});
    }

Now if you fill in the items and submit, the page simply refreshes itelf. We need to get hold of the posted form data and do something useful with it.

This will be what we’ll focus on next time.

Tutorial Recap Part 2

In part 2 of the Node JS tutorial, we started to explore some very basic routing techniques. A number of dedicated routing modules have sprung up, of two of which are listed here:

• Tim Caswell’s node-router
• Tom Hughes-Croucher’s node-routing
• Find more on the Node Modules wiki page

Complete Code

var sys = require('sys'),
    fs = require('fs'),
    http = require('http'),
    url = require('url');
 
// Node-CouchDB: http://github.com/felixge/node-couchdb
var couchdb = require('./libs/node-couchdb/lib/couchdb'),
    client = couchdb.createClient(5984, 'localhost'),
    db = client.db('erdnodeflips');
 
// Haml-js: http://github.com/creationix/haml-js
var haml = require('./libs/haml-js/lib/haml');
 
var doc_id = '2d36f401bc4b82c9160e1a4ea936aba3';
 
http.createServer(function (req, res) {
    var url_parts = url.parse(req.url);
 
    switch(url_parts.pathname) {
    case '/':
	display_root(url_parts.pathname, req, res);
	break;
    case '/create':
	display_create(url_parts.pathname, req, res);
	break;
    case '/edit':
	sys.puts("display edit");
	break;
    default:
	display_404(url_parts.pathname, req, res);
    }
    return;
 
    /**
     * Display the document root
     **/
    function display_root(url, req, res) {
	res.writeHead(200, {'Content-Type': 'text/html'});
	db.getDoc(doc_id, function(error, doc) {
	    if(error) {
		fs.readFile('./templates/no-doc.haml', function(e, c) {
		    var data = {
			title: "No Document Found",
			message: "No document could be found",
			link: "/create",
			link_text: "Create a new document"
		    };
		    var html = haml.render(c.toString(), {locals: data});
		    res.end(html);
		});
	    }
	    else {
		fs.readFile('./templates/doc.haml', function(e, c) {
		    var data = {
			title: "Erdnodeflip document: "+doc.name,
			message: "Your Erdnusflip document was found!",
			items: doc.items,
		    };
		    var html = haml.render(c.toString(), {locals: data});
		    res.end(html);
		});
	    }
	});
    }
 
    /**
     * Display the list creat page
     **/
    function display_create(url, req, res) {
	res.writeHead(200, {'Content-Type': 'text/html'});
	fs.readFile('./templates/create.haml', function(e, c) {
	    var data = {
		title: "Create New List",
		message: "Please enter up to 5 things to remember",
		url: url
	    };
	    var html = haml.render(c.toString(), {locals: data});
	    res.end(html);
	});
    }
 
    /**
     * Display the 404 page for content that can't be found
     **/
    function display_404(url, req, res) {
	res.writeHead(404, {'Content-Type': 'text/html'});
	res.write("
<h1>404 Not Found</h1>
");
	res.end("
 
The page you were looking for: "+url+" can not be found");
    }
}).listen(8000);
sys.puts('Server running at http://127.0.0.1:8000/');

1. To list a number of items
2. To remove an item from the list
3. To add an item to the list

Obviously, before getting cracking with this tutorial I had to think up a name for this “killer app” of the Node world.

So I give you ErdNodeFlips! In honour of erdnussflips – the strangely addictive Wotsit type things that taste of peanut butter and stick to the top of your mouth. Yum! (OMG – they even have their own Facebook page!)

All code is available on GitHub.

Directory Structure and Libraries

The first step is to create a directory structure for the application and bring in the relevant libraries. We need two directories underneath the top-level application root: templates (which will hold the haml files) and libs (which will contain 3rd party libraries). We are going to grab two libraries off GitHub:

• Felix Geisendörfer’s node-couchdb – this is what we’ll be using to interact with the Couch database
• Tim Caswell’s haml-js – this is our haml template engine

$ cd /
$ mkdir {libs,templates}
$ cd libs
$ git clone git://github.com/felixge/node-couchdb.git
$ git clone http://github.com/creationix/haml-js.git
$ cd ../

Basic Web Server

Now we can get started. Open up a new file called main.js in your favourite editor. Now, just to make sure that everything is working at this early stage you can copy and paste the http server example from the nodejs.org front page and run that.

http.createServer(function (req, res) {
  setTimeout(function () {
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('Hello World\n');
  }, 2000);
}).listen(8000);

$ node ./main.js

Navigate to http://127.0.0.1:8000/ and after 2 seconds you should see “Hello World” appear. If you see this, all is working. We have the (very basic) base of our application.

Talk to the Database

Once we know that our basic setup is working, we can try and interact with the database. Before we can do this, however, we actually need to create the database and add an record – or document.

CouchDB comes with a nifty little utility called Futon. We’ll use this to quickly create our database and add a document.

• Go to http://localhost:5984/_utils/
• Create a new database: erdnodeflips
• Create a new document
• Add Field – name it name
• Double click on the value for name, enter “Don’t forget” (including the quotes)
• Add another field – name it items
• Double click on the value for items enter: ["item 1", "item 2", "item 3"] (including quotes and square brackets)
• Click on Save Document – copy the _id value
• Navigate to: http://localhost:5984/erdnodeflips/[value of "_id"] to see something like: {”_id”:”2d36f401bc4b82c9160e1a4ea936aba3″,”_rev”:”2-3b9f738a50ff9928348ce32b0eb807b2″,”items”:["item 1","item 2","item 3"],”name”:”Rob’s List”}

To read this within node we simply need to know the _id of the document. Save this as a var for now:

var doc_id = ‘2d36f401bc4b82c9160e1a4ea936aba3′;

and replace the setTimeout function with the following:

db.getDoc(doc_id, function(error, doc) {
	if(error) {
	    res.write(JSON.stringify(error));
	}
	else {
	    res.write('Fetched my new doc from couch:');
	    res.write(JSON.stringify(doc));
	}
     res.end("-= Fin =-");
    });

This is pretty simple, and should be relatively straight forward to read. Essentially the code tries to get the document identified by doc_id, invoking a function when done: db.getDoc(doc_id, function(error, doc){});

The function that is invoked has 2 arguments, one containing the error (if any) and the second containing the actual document returned (if any).

Within this function we can then deal with the two arguments as needed. If there is an error, we output that to the browser, if no error and a doc is returned, output that instead.

Finally, we end the server response: res.end(”-= Fin =-”);. Note, we must end the server response within the callback of the getDoc() function. Due to the event driven, asynchronous nature of Node, if we end the response after that function then the server response will more than likely be closed before getDoc() has had a chance to write the additional server responses.

So the code now looks like this:

var sys = require('sys'),
    fs = require('fs'),
    http = require('http');
 
// Node-CouchDB: http://github.com/felixge/node-couchdb
var couchdb = require('./libs/node-couchdb/lib/couchdb'),
    client = couchdb.createClient(5984, 'localhost'),
    db = client.db('erdnodeflips');
 
// Haml-js: http://github.com/creationix/haml-js
var haml = require('./libs/haml-js/lib/haml');
 
var doc_id = '2d36f401bc4b82c9160e1a4ea936aba3';
 
http.createServer(function (req, res) {
    res.writeHead(200, {'Content-Type': 'text/html'});
    db.getDoc(doc_id, function(error, doc) {
	if(error) {
	    res.write(JSON.stringify(error));
	}
	else {
	    res.write('Fetched my new doc from couch:');
	    res.write(JSON.stringify(doc));
	}
     res.end("-= Fin =-");
    });
 
}).listen(8000);
sys.puts('Server running at http://127.0.0.1:8000/');

Generate Nicer Output

If you run the above code, you should get something along the lines of:

Fetched my new doc from couch:{”_id”:”2d36f401bc4b82c9160e1a4ea936aba3″,”_rev”:”2-3b9f738a50ff9928348ce32b0eb807b2″,”items”:["item 1","item 2","item 3"],”name”:”Rob’s List”}-= Fin =-

So it works, but it doesn’t look very good.

First, lets create a Haml template that we can use to output something better.

!!! Strict
%html(lang="en")
  %head
    %title&= title
  %body
    %h1&= title
    %p&= message
    :if items.length === 0
      %p There are no items to remember
    :if items.length > 0
      %ul
        :each item in items
          %li&=

I’m not going to go into great depth. You can find more information on Haml at the Haml homepage and also have a look at Tim’s excellent tutorial on his Haml-js library.

Essentially, this template is going to build an XHTML strict page that will have a title, a message and then should loop through the items in the list. To get this displayed, we then need to open up the template file, render it and then output it as a server response. The code to do that is:

fs.readFile('./templates/doc.haml', function(e, c) {
		var data = {
		    title: "Erdnodeflip document: "+doc.name,
		    message: "Your Erdnusflip document was found!",
		    items: doc.items,
		};
		var html = haml.render(c.toString(), {locals: data});
		res.end(html);
	    });

Notice that I am simply ending the response with the generated HTML. Again, it is worth keeping an eye on exactly where the response is being ended otherwise you might find you are trying to add to a conversation that has already ended.

We can do the same for the “document not found” route:

!!! Strict
%html(lang="en")
  %head
    %title&= title
  %body
    %h1&= title
    %p&= message
    %p %a{href: link}&= link_text

fs.readFile('./templates/no-doc.haml', function(e, c) {
		var data = {
		    title: "No Document Found",
		    message: "No document could be found",
		    link: "/create",
		    link_text: "Create a new document"
		};
		var html = haml.render(c.toString(), {locals: data});
		res.end(html);

Quick Recap for this Tutorial

In this tutorial we’ve only scratched the surface of what can be done. However, in a relatively short space of time we have our Node web server communicating with a CouchDB database and displaying some valid strict XHTML. Not bad for one sitting!

To recap, our code now looks like this:

var sys = require('sys'),
    fs = require('fs'),
    http = require('http');
 
// Node-CouchDB: http://github.com/felixge/node-couchdb
var couchdb = require('./libs/node-couchdb/lib/couchdb'),
    client = couchdb.createClient(5984, 'localhost'),
    db = client.db('erdnodeflips');
 
// Haml-js: http://github.com/creationix/haml-js
var haml = require('./libs/haml-js/lib/haml');
 
var doc_id = '2d36f401bc4b82c9160e1a4ea936aba3';
 
http.createServer(function (req, res) {
    res.writeHead(200, {'Content-Type': 'text/html'});
    db.getDoc(doc_id, function(error, doc) {
	if(error) {
	    fs.readFile('./templates/no-doc.haml', function(e, c) {
		var data = {
		    title: "No Document Found",
		    message: "No document could be found",
		    link: "/create",
		    link_text: "Create a new document"
		};
		var html = haml.render(c.toString(), {locals: data});
		res.end(html);
	    });
	}
	else {
	    fs.readFile('./templates/doc.haml', function(e, c) {
		var data = {
		    title: "Erdnodeflip document: "+doc.name,
		    message: "Your Erdnusflip document was found!",
		    items: doc.items,
		};
		var html = haml.render(c.toString(), {locals: data});
		res.end(html);
	    });
	}
    });
 
}).listen(8000);
sys.puts('Server running at http://127.0.0.1:8000/');

The exciting thing here is that we’ve thrown in a link! However, if you click on it, it will simply reload the page.

Being able to handle this kind of basic page navigation and actually adding stuff to the database is for next time.

Feedback always welcome. You can find all the code on my GitHub pages.

Valuable Node resources:

• The official Node JS site
• The Node Github page
• How To Node – a great place for tutorials and other tips
• Node Blogs – which appears to be down at the moment, but again is very useful
• NodeJS Google Group – keep your finger on the pulse