Welcome!

Apache Authors: William Schmarzo, Christopher Harrold, Elizabeth White, Talend Inc., Adrian Bridgwater

Blog Feed Post

The Absolute Beginner’s Guide to Node.js

An absolute Beginner's Guide to node.js – by Brandon Cannaday

This is a republished blog post by Brandon Cannaday. Brandon is the CTO of Modulus, a Node.js application hosting platform. Brandon organizes the Indianapolis Node.js meetup and enjoys speaking at conferences about Node’s horizontal scalability. Prior to Modulus, Brandon worked in the chemical detection and telecommunications industries.

Modulus is the first company in the industry to offer a dedicated enterprise solution called Curvature. Curvature allows you to take advantage of rapid deployments, easy scaling, and real-time analytics in the environment of your choosing, on-premises, in the cloud, or a hybrid of the two.


There’s no shortage of Node.js tutorials out there, but most of them cover specific use cases or topics that only apply when you’ve already got Node up and running. I see comments every once and awhile that sound something like, “I’ve downloaded Node, now what?” This tutorial answers that question and explains how to get started from the very beginning.

What is Node.js?

A lot of the confusion for newcomers to Node is misunderstanding exactly what it is. The description on nodejs.org definitely doesn’t help.

An important thing to realize is that Node is not a webserver. By itself it doesn’t do anything. It doesn’t work like Apache. There is no config file where you point it to you HTML files. If you want it to be a HTTP server, you have to write an HTTP server (with the help of its built-in libraries). Node.js is just another way to execute code on your computer. It is simply a JavaScript runtime.

Installing Node

Node.js is very easy to install. If you’re using Windows or Mac, installers are available on the download page.

I’ve Installed Node, now what?

Once installed you’ll have access to a new command called “node”. You can use the node command in two different ways. The first is with no arguments. This will open an interactive shell (REPL: read-eval-print-loop) where you can execute raw JavaScript code.

$ node
> console.log('Hello World');
Hello World
undefined

An absolute Beginner's Guide to node.js – Hello World

In the above example I typed “console.log(‘Hello World’)” into the shell and hit enter. Node will then execute that code and we can see our logged message. It also prints “undefined” because it displays the return value of each command and console.log doesn’t return anything.

The other way to run Node is by providing it a JavaScript file to execute. This is almost always how you’ll be using it.

hello.js

console.log('Hello World');
$ node hello.js
Hello World

An absolute Beginner's Guide to node.js – console

In this example, I moved the console.log message into a file then passed that file to the node command as an argument. Node then runs the JavaScript in that file and prints “Hello World”.

File I/O with node.js

Running plain JavaScript is fun and all, but not very useful. This is why Node.js also includes a powerful set of libraries (modules) for doing real things. In this first example I’m going to open a log file and parse it.

example_log.txt

2013-08-09T13:50:33.166Z A 2
2013-08-09T13:51:33.166Z B 1
2013-08-09T13:52:33.166Z C 6
2013-08-09T13:53:33.166Z B 8
2013-08-09T13:54:33.166Z B 5

What this log data means is not important, but basically each message contains a date, a letter, and a value. I want to add up the values for each letter.

The first thing we need to do it read the contents of the file.

my_parser.js

// Load the fs (filesystem) module
var fs = require('fs');

// Read the contents of the file into memory.
fs.readFile('example_log.txt', function (err, logData) {

// If an error occurred, throwing it will
  // display the exception and end our app.
  if (err) throw err;

// logData is a Buffer, convert to string.
  var text = logData.toString();
});

Fortunately Node.js makes file I/O really easy with the built-in filesystem (fs) module. The fs module has a function named readFile that takes a file path and a callback. The callback will be invoked when the file is done being read. The file data comes in the form of a Buffer, which is basically a byte array. We can convert it to a string using the toString() function.

Now let’s add in the parsing. This is pretty much normal JavaScript so I won’t go into any details.

my_parser.js

// Load the fs (filesystem) module.
var fs = require('fs');// 

Read the contents of the file into memory.
fs.readFile('example_log.txt', function (err, logData) {

// If an error occurred, throwing it will
  // display the exception and kill our app.
  if (err) throw err;

// logData is a Buffer, convert to string.
  var text = logData.toString();

var results = {};

// Break up the file into lines.
  var lines = text.split('\n');

lines.forEach(function(line) {
    var parts = line.split(' ');
    var letter = parts[1];
    var count = parseInt(parts[2]);

if(!results[letter]) {
      results[letter] = 0;
    }

results[letter] += parseInt(count);
  });

console.log(results);
  // { A: 2, B: 14, C: 6 }
});

Now when you pass this file as the argument to the node command it will print the result and exit.

$ node my_parser.js
{ A: 2, B: 14, C: 6 }

An absolute Beginner's Guide to node.js – my_parser.js

I use Node.js a lot for scripting like this. It’s much easier and a more powerful alternative to bash scripts.

Asynchronous Callbacks in node.js

As you saw in the previous example, the typical pattern in Node.js is to use asynchronous callbacks. Basically you’re telling it to do something and when it’s done it will call your function (callback). This is because Node is single-threaded. While you’re waiting on the callback to fire, Node can go off and do other things instead of blocking until the request is finished.

This is especially important for web servers. It’s pretty common in modern web applications to access databases. While you’re waiting for the database to return results Node can process more requests. This allows you to handle thousands of concurrent connections with very little overhead, compared to creating a separate thread for each connection.

Create a HTTP Server with node.js

Like I said before Node doesn’t do anything out of the box. One of the built-in modules makes it pretty easy to create a basic HTTP server, which is the example on the Node.js homepage.

my_web_server.js

var http = require('http');

http.createServer(function (req, res) {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('Hello World\n');
}).listen(8080);

console.log('Server running on port 8080.');

When I say basic, I mean basic. This is not a full-featured HTTP server. It can’t serve any HTML file or images. In fact, no matter what you request, it will return ‘Hello World’. However, you can run this and hit http://localhost:8080 in your browser and you’ll see the text.

$ node my_web_server.js

You might notice something a little different now. Your Node.js application no longer exits. This is because you created a server and your Node.js application will continue to run and respond to requests until you kill it yourself.

If you want this to be a full-featured web server, then you have to do that work. You have to check what was requested, read the appropriate files, and send the content back. There’s good news, though. People have already done this hard work for you.

Express for node.js

Express is a framework that makes creating most normal websites very simple. The first thing you have to do it install it. Along with the node command you also have access to a command called “npm”. This tool gives you access to an enormous collection of modules created by the community, and one of them is Express.

$ cd /my/app/location
$ npm install express

When you install a module, it will put it in a node_modules folder inside your application directory. You can now require it like any built-in module. Let’s create a basic static file server using Express.

my_static_file_server.js

var express = require('express'),
    app = express();

app.use(express.static(__dirname + '/public'));

app.listen(8080);
$ node my_static_file_server.js

You now have a pretty capable static file server. Anything you put in the /public folder can now be requested by your browser and displayed. HTML, images, almost anything. So for example, if you put an image called “my_image.png” inside the public folder, you can access it using your browser by going to http://localhost:8080/my_image.png. Of course Express has many many more features, but you can look those up as you continue developing.

NPM

We touched on npm a little in the previous section, but I want to emphasize how important this tool will be to normal Node.js development. There are thousands of modules available that solve almost all typical problems that you’re likely to encounter. Remember to check npm before re-inventing the wheel. It’s not unheard of for a typical Node.js application to have dozens of dependencies.

In the previous example we manually installed Express. If you have a lot of dependencies, that’s not going to be a very good way to install them. That’s why npm makes use of a package.json file.

package.json

{
  "name" : "MyStaticServer",
  "version" : "0.0.1",
  "dependencies" : {
    "express" : "3.3.x"
  }
}

A package.json file contains an overview of your application. There are a lot of available fields, but this is pretty much the minimum. The dependencies section describes the name and version of the modules you’d like to install. In this case I’ll accept any version of Express 3.3. You can list as many dependencies as you want in this section.

Now instead of installing each dependency separately, we can run a single command and install all of them.

$ npm install

When you run this command npm will look in the current folder for a package.json file. If it finds one, it will install every dependency listed.

Code Organization in node.js

So far we’ve only been using a single file, which isn’t very maintainable. In most applications your code will be split into several files. There’s no standard or enforced organization to what files go where. This isn’t Rails. There’s no concept of views go here and controllers go there. You can do whatever you want.

Let’s re-factor the log parsing script. It’s much more testable and more maintainable if we separate out the parsing logic into its own file.

parser.js

// Parser constructor.
var Parser = function() {

};

// Parses the specified text.
Parser.prototype.parse = function(text) {

var results = {};

// Break up the file into lines.
  var lines = text.split('\n');

lines.forEach(function(line) {
    var parts = line.split(' ');
    var letter = parts[1];
    var count = parseInt(parts[2]);

if(!results[letter]) {
      results[letter] = 0;
    }

results[letter] += parseInt(count);
  });

return results;
};

// Export the Parser constructor from this module.
module.exports = Parser;

What I did was create a new file to hold the logic for parsing logs. This is just standard JavaScript and there are many ways to encapsulate this code. I chose to define a new JavaScript object because it’s easy to unit test.

The important piece to this is the “module.exports” line. This tells Node what you’re exporting from this file. In this case I’m exporting the constructor, so users can create instances of my Parser object. You can export whatever you want.

Now let’s look at how to import this file and make use of my new Parser object.

my_parser.js

// Require my new parser.js file.
var Parser = require('./parser');

// Load the fs (filesystem) module.
var fs = require('fs');

// Read the contents of the file into memory.
fs.readFile('example_log.txt', function (err, logData) {

// If an error occurred, throwing it will
  // display the exception and kill our app.
  if (err) throw err;

// logData is a Buffer, convert to string.
  var text = logData.toString();

// Create an instance of the Parser object.
  var parser = new Parser();

// Call the parse function.
  console.log(parser.parse(text));
  // { A: 2, B: 14, C: 6 }
});

Files are included exactly like modules, except you provide a path instead of a name. The .js extension is implied so you can leave it off if you want.

Since I exported the constructor that is what will be returned from the require statement. I can now create instances of my Parser object and use it.

Summary

Hopefully this tutorial can bridge the gap between downloading Node.js and building your first widget. Node.js is an extremely powerful and flexible technology that can solve a wide variety of problems.

I want everyone to remember that Node.js is only bound by your imagination. The core libraries are very carefully designed to provide the puzzle pieces needed to build any picture. Combine those with the modules available in npm and it’s amazing how quickly you can begin building very complex and compelling applications.

If you have any questions or comments, feel free to drop them below.

Codeship – A hosted Continuous Deployment platform for web applications

Now you know how to get started with node.js why don’t you head over to Codeship and set up Continuous Deployment your first node.js project?

Read the original blog entry...

More Stories By Manuel Weiss

I am the cofounder of Codeship – a hosted Continuous Integration and Deployment platform for web applications. On the Codeship blog we love to write about Software Testing, Continuos Integration and Deployment. Also check out our weekly screencast series 'Testing Tuesday'!

@ThingsExpo Stories
SYS-CON Events announced today TechTarget has been named “Media Sponsor” of SYS-CON's 18th International Cloud Expo, which will take place on June 7–9, 2016, at the Javits Center in New York City, NY, and the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. TechTarget is the Web’s leading destination for serious technology buyers researching and making enterprise technology decisions. Its extensive global networ...
SoftLayer operates a global cloud infrastructure platform built for Internet scale. With a global footprint of data centers and network points of presence, SoftLayer provides infrastructure as a service to leading-edge customers ranging from Web startups to global enterprises. SoftLayer's modular architecture, full-featured API, and sophisticated automation provide unparalleled performance and control. Its flexible unified platform seamlessly spans physical and virtual devices linked via a world...
SYS-CON Events announced today that Commvault, a global leader in enterprise data protection and information management, has been named “Bronze Sponsor” of SYS-CON's 18th International Cloud Expo, which will take place on June 7–9, 2016, at the Javits Center in New York City, NY, and the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Commvault is a leading provider of data protection and information management...
SYS-CON Events announced today that BMC Software has been named "Siver Sponsor" of SYS-CON's 18th Cloud Expo, which will take place on June 7-9, 2015 at the Javits Center in New York, New York. BMC is a global leader in innovative software solutions that help businesses transform into digital enterprises for the ultimate competitive advantage. BMC Digital Enterprise Management is a set of innovative IT solutions designed to make digital business fast, seamless, and optimized from mainframe to mo...
SYS-CON Events announced today that Tintri Inc., a leading producer of VM-aware storage (VAS) for virtualization and cloud environments, will exhibit at the 18th International CloudExpo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, New York, and the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.
SYS-CON Events announced today BZ Media LLC has been named “Media Sponsor” of SYS-CON's 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. BZ Media LLC is a high-tech media company that produces technical conferences and expositions, and publishes a magazine, newsletters and websites in the software development, SharePoint, mobile development and Commercial Drone markets.
SYS-CON Events announced today that MangoApps will exhibit at SYS-CON's 18th International Cloud Expo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. MangoApps provides modern company intranets and team collaboration software, allowing workers to stay connected and productive from anywhere in the world and from any device. For more information, please visit https://www.mangoapps.com/.
A strange thing is happening along the way to the Internet of Things, namely far too many devices to work with and manage. It has become clear that we'll need much higher efficiency user experiences that can allow us to more easily and scalably work with the thousands of devices that will soon be in each of our lives. Enter the conversational interface revolution, combining bots we can literally talk with, gesture to, and even direct with our thoughts, with embedded artificial intelligence, wh...
The IoT is changing the way enterprises conduct business. In his session at @ThingsExpo, Eric Hoffman, Vice President at EastBanc Technologies, discuss how businesses can gain an edge over competitors by empowering consumers to take control through IoT. We'll cite examples such as a Washington, D.C.-based sports club that leveraged IoT and the cloud to develop a comprehensive booking system. He'll also highlight how IoT can revitalize and restore outdated business models, making them profitable...
SYS-CON Events announced today that ContentMX, the marketing technology and services company with a singular mission to increase engagement and drive more conversations for enterprise, channel and SMB technology marketers, has been named “Sponsor & Exhibitor Lounge Sponsor” of SYS-CON's 18th Cloud Expo, which will take place on June 7-9, 2016, at the Javits Center in New York City, New York. “CloudExpo is a great opportunity to start a conversation with new prospects, but what happens after the...
The essence of data analysis involves setting up data pipelines that consist of several operations that are chained together – starting from data collection, data quality checks, data integration, data analysis and data visualization (including the setting up of interaction paths in that visualization). In our opinion, the challenges stem from the technology diversity at each stage of the data pipeline as well as the lack of process around the analysis.
The 19th International Cloud Expo has announced that its Call for Papers is open. Cloud Expo, to be held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, brings together Cloud Computing, Big Data, Internet of Things, DevOps, Containers, Microservices and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding business opportunity. Submit y...
Internet of @ThingsExpo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with the 19th International Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world and ThingsExpo New York Call for Papers is now open.
Designing IoT applications is complex, but deploying them in a scalable fashion is even more complex. A scalable, API first IaaS cloud is a good start, but in order to understand the various components specific to deploying IoT applications, one needs to understand the architecture of these applications and figure out how to scale these components independently. In his session at @ThingsExpo, Nara Rajagopalan is CEO of Accelerite, will discuss the fundamental architecture of IoT applications, ...
In his session at 18th Cloud Expo, Bruce Swann, Senior Product Marketing Manager at Adobe, will discuss how the Adobe Marketing Cloud can help marketers embrace opportunities for personalized, relevant and real-time customer engagement across offline (direct mail, point of sale, call center) and digital (email, website, SMS, mobile apps, social networks, connected objects). Bruce Swann has more than 15 years of experience working with digital marketing disciplines like web analytics, social med...
SYS-CON Events announced today that Enzu, a leading provider of cloud hosting solutions, will exhibit at SYS-CON's 18th International Cloud Expo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. Enzu’s mission is to be the leading provider of enterprise cloud solutions worldwide. Enzu enables online businesses to use its IT infrastructure to their competitive advantage. By offering a suite of proven hosting and management services, Enzu wants companies to foc...
Customer experience has become a competitive differentiator for companies, and it’s imperative that brands seamlessly connect the customer journey across all platforms. With the continued explosion of IoT, join us for a look at how to build a winning digital foundation in the connected era – today and in the future. In his session at @ThingsExpo, Chris Nguyen, Group Product Marketing Manager at Adobe, will discuss how to successfully leverage mobile, rapidly deploy content, capture real-time d...
IoT generates lots of temporal data. But how do you unlock its value? How do you coordinate the diverse moving parts that must come together when developing your IoT product? What are the key challenges addressed by Data as a Service? How does cloud computing underlie and connect the notions of Digital and DevOps What is the impact of the API economy? What is the business imperative for Cognitive Computing? Get all these questions and hundreds more like them answered at the 18th Cloud Expo...
As cloud and storage projections continue to rise, the number of organizations moving to the cloud is escalating and it is clear cloud storage is here to stay. However, is it secure? Data is the lifeblood for government entities, countries, cloud service providers and enterprises alike and losing or exposing that data can have disastrous results. There are new concepts for data storage on the horizon that will deliver secure solutions for storing and moving sensitive data around the world. ...
What a difference a year makes. Organizations aren’t just talking about IoT possibilities, it is now baked into their core business strategy. With IoT, billions of devices generating data from different companies on different networks around the globe need to interact. From efficiency to better customer insights to completely new business models, IoT will turn traditional business models upside down. In the new customer-centric age, the key to success is delivering critical services and apps wit...