Table of Contents
1. Introduction to Node.js
One of the core characteristics of Node.js, which makes it highly sought-after by businesses looking to hire Node.js developers, is its non-blocking, event-driven architecture. This key feature enables Node.js to handle concurrent requests efficiently. Consequently, it is ideal for developing real-time applications such as chat platforms, gaming servers, collaborative tools, and streaming services. Therefore, when you hire Node.js developers, you are investing in professionals capable of leveraging this unique architecture to build fast, efficient and scalable applications.
2. Setting Up Node.js
Before diving into the code, we need to ensure that Node.js is installed on your system. You can download and install it from the official Node.js website. Once installed, you can verify the installation by opening your terminal or command line and typing:
```bash node -v ```
This command should return the installed version of Node.js.
3. Understanding The Basics
3.1 Hello World in Node.js
Now that we have Node.js installed, let’s create our first Node.js application – a traditional “Hello, World!” example. Create a new file called `app.js` and add the following lines of code:
You can run this Node.js program by opening your terminal or command line, navigating to the directory where you saved `app.js`, and typing:
```bash node app.js ```
3.2 Importing Modules in Node.js
Let’s use the HTTP module, a built-in Node.js module, to create a simple server:
In this code, the `require` function is used to include the HTTP module. The `http.createServer()` method creates a server that listens on port 8080. When you open your browser and navigate to `http://localhost:8080`, you should see “Hello, World!”.
4. Asynchronous Programming and Callbacks
A key part of mastering Node.js involves understanding asynchronous programming. Unlike traditional synchronous programming, where operations are performed one after another, asynchronous operations can execute concurrently.
In Node.js, most I/O operations (like reading from the network, accessing a database, or querying the filesystem) are performed asynchronously. Callbacks are often used to handle these operations. A callback is a function passed to another function as an argument and is executed after the parent function has completed.
Here’s an example of reading a file asynchronously using the `fs` (file system) module in Node.js:
In this example, `fs.readFile` is an asynchronous function that reads a file and then uses a callback to print the file contents. The ‘Reading file…’ message will be displayed before the file contents, demonstrating the non-blocking nature of Node.js.
5. Event-Driven Programming
Node.js is inherently event-driven, meaning it uses events and event handlers to drive its architecture. An event can be anything from a user clicking a button to a server receiving a request. When an event occurs, an event handler (or callback) is invoked to handle that event.
The `events` module allows us to create and handle custom events:
Here, an event called ‘scream’ is created. When this event is fired using `eventEmitter.emit(‘scream’)`, the handler function `myEventHandler` is called.
6. Express.js: A Fast Opinionated Web Framework
Express.js is a lightweight, flexible Node.js web application framework that provides a robust set of features for building single-page, multi-page, and hybrid web applications. It simplifies the process of building web applications by providing easy-to-use methods for routing, middleware configuration, and template engine setup.
Here’s an example of creating a basic Express.js application:
In this example, when you navigate to `http://localhost:3000` in your browser, you’ll see the text “Hello World!”.