Node.js Assignment Help

Node JS is an Open source available for everyone, Cross platform can run on any platform and Runtime environment for server-side and network application which built on Google chrome’s V8 JavaScript engine.

History

It was developed in 2009 by Ryan Dahl. All the application in the node.js written in Javascript and run on Microsoft windows and Linux. It also provide rich library which is a javascript library and that extend the Node.js application.

Why use Node.js?

Nowadays JavaScript is rising popularity with uncountable changes in web development. Today, we can run JavaScript on the server as well on the browser. As this is more benefit of JavaScript than Node.js. It is a packaged compilation of Google’s V8 JavaScript engine and libuv platform abstraction layer and the core library of javascript. Node.js is high above in real-time web application that employ push technologies over websockets. After 20 years of stateless paradigm now we have a web application which is two-way connection in which both client and server can initiate communication that allowing them to exchange data freely. Or, they run in isolation and operated over non-standard ports, which require extra permission.

Features of Node.js

Following are some features.

• License: Node.js released under the MIT license.
• Very fast: It is very fast in code execution because it built on Google Chrome’s Engine.
• Single threaded but highly scalable: Support single threaded model with the event looping and the server is highly scalable because the concept of event mechanism helps the server to respond in non- blocking way.
• Asynchronous and Event Driven: Node.js based server never waits for an API to return data, after calling it once it move to another API and collect all the notifications mechanism that helps to get response from previous API call.
• No buffering: Node.js never buffer any data output data in chunks.

Variables in Node.js

Process of variables in the node.js environment is available in process.env which is most common case in NODE_ENV
By using NODE_ENV variable

process.env.NODE_ENV = process.env.NODE_ENV || 'development';

if (process.env.NODE_ENV === 'development') {  
  developmentTasks();
} else if (process.env.NODE_ENV === 'production') {
  productionTasks();
}

Strings in node.js

If we talk about strings in node.js then string.js is a lightweight JavaScript library for the browser as well as for node.js which provides extra String Methods and modify string prototype. If we do experiments on string.js, just simple open the webkit inspector in either Chrome or safari, or on the web console in firefox so you will see string.js is already included and you start doing experiments on it.

var S = require('string');

Numbers in node.js

Numbers is the advanced mathematics toolkit used in node.js which provide a comprehensive sets of mathematical tools which is not currently offered by JavaScript. Tools include: Basic calculation, Calculus, matrix operation, prime numbers, statics and so on. A new and very few things about Node.js is it does not necessarily manage floating points. It uses the primary use cases which is a client side operation which the DOM will recognize it can also be used by Data analysis, calculation on the server.

var numbers = require('numbers');

Functions in node.js

A callback is asynchronous equivalent for a function which is also called a completion of the given task. All the API’s of node are written in such a way that they support callbacks. Let take an example to clearly understand the concept of callback: A function once read a file give control to execution environment so that next instruction can execute and once the file I/O complete then it will call the callback function in which file’s content is a parameter of the function and there is no blocking for File I/O. This make scalable Node.js and can process high number of request without waiting for any function.

Non-Blocking Code Example

//Create a text file named input.txt having following content
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//Update main.js file to have following code:

var fs = require("fs");

fs.readFile('input.txt', function (err, data) {
    if (err) return console.error(err);
    console.log(data.toString());
});
console.log("Program Ended");

//Now run the main.js to see the result:

$ node main.js

Verify the Output

///Program Ended

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Objects in Node.js

As we know JavaScript is an object-oriented programming language which support delegating inheritance based on prototypes. Each object have a prototype property which refers to another object and that looked up from two places:

• Object itself (Obj.foo).
• And the second one is when property does not exist on the prototype of the object (Obj.prototype.foo).

Assigning to an undefined property of any object will create it and the property of object itself take precedence over properties of prototype. To create new objects new constructor has to be create and look up is performed recursively.

Concept of Delegating inheritance: Concept defines the runtime lookups from the prototype property rather than statically defined class constructs this prototype chain lookup mechanism is prototypal inheritance.

Node-array

Node.js extends the array object to provide more methods and features to operate array objects. By using NPM utility can install module directly. It provide many easy-use methods and features to operate array objects.

[Array Object]forEachasync()
var Array = require('node-array');
var a = [ 1, 2, 3, 4, 5 ];
 
a.forEachAsync(function(element, index, arr) {
console.log(element);
}, function() {
console.log('complete');
});

// Make 50 workers to process all items of array in parallel 
a.parallel(50, function(element, index, arr, complete) {
setTimeout(function() {
console.log(element);
complete();
}, Math.round(Math.random() * 1000));
}, function() {
console.log('complete');
});
[ArrayObject]parallel()
var Array = require('node-array');
 
var a = [];
 
// Prepare 1000 items for testing 
for (var i = 0; i < 1000; i++) {
        a.push(i+1);
}

Event Driven Programming

The reason why Node.js is pretty fast as compared to other technologies is it uses events heavily. Whenever the node server starts it initiates its variables, declare functions and simple wait for the event to occur. There is a loop that listens for event and trigger a callback function when one of the function is detected. There is a different lies between both of the two callback function is called when as asynchronous function return its result where as event handling works on observer patterns. It is a type of function which listen and observe and perform specified task. There are some in-built events available that bind event with event listeners.

// Import events module
var events = require('events');
// Create an eventEmitter object
var eventEmitter = new events.EventEmitter();

// Bind event and even handler as follows
eventEmitter.on('eventName', eventHandler);

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Related Reads of Node.js

• Node.js Package manager(NPM)
• Event Emitter
• Buffers
• Streams
• File System
• Utility Module
• Web Module
• Packaging