NodeJS

Today I wanted to talk about NodeJS. NodeJS is a runtime implemented on Google’s V8 engine and can serve as a great web server. The idea of NodeJS is that you write your logic and start the server from your script. This is different from, for example, ASP.NET where your server is managed by IIS and you just hook into that process.

Oh yeah, before I forget, you write NodeJS applications using JavaScript and if you read this blog you know I’m a big fan of JavaScript when it is done right. The asynchronous nature of JavaScript is perfect for an application build on top of V8. Now let’s dive into the code!

var http = require('http');

function handleRequest(req, res) {
    res.end('Hello World\n');
}

http.createServer(handleRequest).listen(5000, function() {
    console.log('listening on port 5000');
});

This little piece of code is enough to create a simple web server which will retrun the string “Hello World\n” for every request done to this server. Now, you may not think that this is a big deal, but this is huge! A single file with just a dependency loaded through a require statement serves actual content.

How can we test our little server? Well, we could curl it:

curl -X GET http://localhost:5000/

I alwasy like to use little tools and other pieces of code together and work through an otherwise unsolvable problem, but, today I’m going to be lazy and I will jsut open up a browser to get things rolling. When you go to that address you will see “Hello world” written in yoour browser. Now, how can we serve an actual page?

Http requests are build in such a way that headers give extra information about the request and the browser uses this information to render the content which you’ve requested. For example if we want to serve HTML we van specify this like so, in our server write the following code:

var http = require('http');

function handleRequest(req, res) {
    res.end('<h1>This is a header</h1>');
}

http.createServer(handleRequest).listen(5000, function() {
    console.log('listening on port 5000');
});

When you open this page in your browser and look at it’s source you can see that it surrounds the h1 tag we’ve created with propper HTML formatting. But we can’t always rely on the tools to do this formatting for us. We will have to do this ourselves, so how do we serve a fully fledged HTML file?

In steps the fs module in NodeJS. With this module we can read a file and send it out to the browser. Just create a basic index.html file and put the following in there:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Simple page</title>
</head>
<body>
    <h1>Hello World!</h1>
</body>
</html>

To serve this page using just plain old Node you can use the following snippet:

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

function hanldeRequest(req, res) {
    fs.readFile('./index.html', 'utf8', function(err, html) {
        req.writeHead(200, {"Content-Type":"text/html"});
        req.write(html);
        req.end();
    });
}

http.createServer(handleRequest).listen(5000, function() {
    console.log('listening on port 5000');
});

This code show you how to serve a simple static HTML file from our NodeJS server to a client. This does not mean that this is the only way of serving static content. As you can see we have