A Comprehensive Overview of Node.js

What is Node.js :

• Node.js is a cross-platform runtime environment and library for running JavaScript applications outside the browser.

• It is used for creating server-side and networking web applications.

• It is open source and free to use.

• Many of the basic modules of Node.js are written in JavaScript.

• Node.js is mostly used to run real-time server applications.

• Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient, perfect for data-intensive real-time applications that run across distributed devices.?

• Node.js also provides a rich library of various JavaScript modules to simplify the development of web applications.

  1. Node.js = Runtime Environment + JavaScript Library

Different parts of Node.js :

The following diagram specifies some important parts of Node.js:

Features of Node.js :

Following is a list of some important features of Node.js that makes it the first choice of software architects.

1. Extremely fast: Node.js is built on Google Chrome's V8 JavaScript Engine, so its library is very fast in code execution.

2. I/O is Asynchronous and Event Driven: All APIs of Node.js library are asynchronous i.e. non-blocking. So a Node.js based server never waits for an API to return data. The server moves to the next API after calling it and a notification mechanism of Events of Node.js helps the server to get a response from the previous API call. It is also a reason that it is very fast.

3. Single threaded: Node.js follows a single threaded model with event looping.

4. Highly Scalable: Node.js is highly scalable because event mechanism helps the server to respond in a non-blocking way.

5. No buffering: Node.js cuts down the overall processing time while uploading audio and video files. Node.js applications never buffer any data. These applications simply output the data in chunks.

6. Open source: Node.js has an open source community which has produced many excellent modules to add additional capabilities to Node.js applications.

7. License: Node.js is released under the MIT license.

Node.js Console :

The Node.js console module provides a simple debugging console similar to JavaScript console mechanism provided by web browsers.

There are three console methods that are used to write any node.js stream:

1. console.log()

2. console.error()

3. console.warn()

Node.js console.log() :

The console.log() function is used to display simple message on console.

1. console.log('Hello Student');

Open Node.js command prompt and run the following code:

1. node console_example1.js

Ourput: Hello Student

Node.js console.error() :

The console.error() function is used to render error message on console.

1. console.error(new Error('Hell! This is a wrong method.'));

Open Node.js command prompt and run the following code:

1. node console_example3.js

Node.js console.warn()

The console.warn() function is used to display warning message on console.

File: console_example4.js

1. const name = 'John';

2. console.warn(`Don't mess with me ${name}! Don't mess with me!`);

Open Node.js command prompt and run the following code:

1. node console_example4.js

Node.js REPL

• The term REPL stands for Read Eval Print and Loop.

• It specifies a computer environment like a window console or a Unix/Linux shell where you can enter the commands and the system responds with an output in an interactive mode.

REPL Environment

• The Node.js or node come bundled with REPL environm/ent.

• Each part of the REPL environment has a specific work.

1. Read: It reads user's input; parse the input into JavaScript data-structure and stores in memory.

2. Eval: It takes and evaluates the data structure.

3. Print: It prints the result.

4. Loop: It loops the above command until user press ctrl-c twice.

   How to start REPL

You can start REPL by simply running "node" on the command prompt. See this:

You can execute various mathematical operations on REPL Node.js command prompt:

Node.js Simple expressions :

After starting REPL node command prompt put any mathematical expression:

1. Example: \>10+20-5

2. 25

1. Example2: \>10+12 + (5*4)/7

Using variable :

• Variables are used to store values and print later.

• If you don't use var keyword then value is stored in the variable and printed whereas if var keyword is used then value is stored but not printed.

• You can print variables using console.log().

Example:

Node.js Multiline expressions

Node REPL supports multiline expressions like JavaScript. See the following do-while loop example:

var x = 0  

undefined  

> do {  

... x++;  

... console.log("x: " + x);  

... } while ( x < 10 );

Node.js Underscore Variable :

You can also use underscore _ to get the last result.

Example:

Node.js REPL Commands :

Node.js Exit REPL:

Use ctrl + c command twice to come out of Node.js REPL.

What Next?

Node.js Package Manager