Comprehensive Guide to ReactJS, JavaScript Fundamentals, and Web Architecture

Posted on Sep 8, 2024 in Computers

ReactJS

ReactJS is a JavaScript library developed by Facebook for building user interfaces, particularly single-page applications. It focuses on creating fast and interactive UIs through reusable components and efficient state management.

Features

Component-Based Architecture: Encourages reusable, encapsulated components that manage their own logic and state.
Virtual DOM: Enhances performance by minimizing direct DOM updates.
Declarative Syntax: Simplifies UI development by updating the DOM efficiently based on state changes.
Unidirectional Data Flow: Ensures a predictable data flow from parent to child components.
JSX: Allows HTML-like syntax within JavaScript, improving code readability.

Advantages

Performance: Fast updates due to the virtual DOM.
Reusability: Modular components promote code reuse.
Ecosystem: Rich set of tools and libraries (e.g., React Router, Redux).
Community Support: Large, active community with extensive resources and third-party solutions.

JSX (JavaScript XML)

JSX (JavaScript XML) is a syntax extension for JavaScript that looks similar to HTML. It allows developers to write HTML elements and components in a JavaScript file.

Why We Need JSX

Readability: JSX makes it easier to visualize the structure of the UI.
Declarative Nature: It allows developers to describe the UI declaratively, making the code more understandable and easier to maintain.

JavaScript Events and Iterators

Events in JavaScript are actions or occurrences that can be detected by the browser, triggering certain responses in the code. These events are used to make web pages interactive and responsive to user inputs or other activities.

An iterator in JavaScript is an object that provides a mechanism for sequentially accessing the elements of a collection, such as an array or string. It follows the iterator protocol, which defines a next() method that returns an object with two properties: value (the next value in the sequence) and done (a boolean indicating whether the sequence has finished).

ES5 vs. ES6

Syntax

ES6 introduced new syntax, such as let, const, arrow functions, template literals, etc., while ES5 relies on older syntax.

Classes

ES6 introduced classes as syntactic sugar over prototypal inheritance.

Modules

ES6 supports the import/export syntax for modules, while ES5 requires external libraries (e.g., RequireJS).

Arrow Functions

Introduced in ES6, they provide a shorter syntax and do not bind their own this.

Block Scoping

let and const in ES6 allow block-level scoping, unlike var in ES5.

JavaScript Promises

A Promise in JavaScript is an object representing the eventual completion or failure of an asynchronous operation. Promises provide a cleaner alternative to callbacks for handling asynchronous tasks.

Methods

then(): Executes when the promise is fulfilled (resolved).
catch(): Executes when the promise is rejected (failed).
finally(): Executes after the promise is settled (either fulfilled or rejected), regardless of the outcome.

Arrow Functions vs. Parameterized Functions

Feature	Arrow Function	Parameterized Function
Syntax	Uses `=>` for a concise syntax.	Traditional function declaration syntax.
this Binding	Lexically binds `this` (inherits from surrounding context).	Binds `this` dynamically based on how the function is called.
Return Values	Implicit return for single expressions without curly braces.	Requires an explicit `return` statement.
Constructor Support	Cannot be used as a constructor (no `new`).	Can be used as constructors.
Arguments Object	Does not have its own `arguments` object; use rest parameters (`...args`).	Has its own `arguments` object.
Usage	Ideal for callbacks, array methods, and simple operations.	Suitable for a wider range of scenarios, including object methods and constructors.

For Loop vs. For…of Loop

Feature	For Loop	For…of Loop
Purpose	General-purpose, used for iterating with control over index and conditions.	Specifically iterates over values of iterable objects like arrays and strings.
Syntax	`for (let i = 0; i < array.length; i++) { console.log(array[i]); }`	`for (let value of array) { console.log(value); }`
Iteration	Iterates based on a manual counter or index.	Automatically iterates over values, no need for index management.
Use Case	Best for complex iteration patterns or when index access is needed.	Ideal for simple, value-focused iteration over iterables.
Applicability	Works with any iterable or even non-iterables.	Limited to iterable objects.

3-Tier Web Architecture

The 3-tier web architecture divides a web application into three layers:

Presentation Layer: This is the front-end layer where users interact with the application through a web browser. It handles the user interface and user experience.
Application Layer: This middle layer contains the business logic of the application. It processes user inputs received from the presentation layer and performs necessary operations, such as calculations or data manipulations.
Data Layer: This layer manages data storage and retrieval. It interacts with databases to store and fetch data as requested by the application layer.

HTTP (Hypertext Transfer Protocol)

HTTP (Hypertext Transfer Protocol) is a protocol used for transferring data over the web. It defines how messages are formatted and transmitted and how web servers and browsers respond to various commands.

HTTP Methods

Common methods include:

GET (retrieve data)
POST (submit data)
PUT (update data)
DELETE (remove data)

HTTPS (Hypertext Transfer Protocol Secure)

HTTPS (Hypertext Transfer Protocol Secure) is HTTP with an added layer of security using SSL/TLS to encrypt the data exchanged between the browser and the server, ensuring confidentiality and integrity.

HTTP Request

A message sent from the client to the server, consisting of:

A request line (method, URL, and HTTP version)
Headers (metadata about the request)
An optional body (data sent to the server)

HTTP Response

A message sent from the server to the client, including:

A status line (HTTP version, status code, and status message)
Headers (metadata about the response)
An optional body (the content requested)

Client-Server Handshake Mechanism in SSL/TLS Protocol

The handshake process in SSL/TLS involves several steps:

Client Hello: The client sends a message to initiate a secure session, including supported protocols and encryption methods.
Server Hello: The server responds with its chosen protocol and encryption methods, along with its digital certificate for authentication.
Key Exchange: Both parties exchange keys or perform operations to establish a shared secret.
Session Established: Once both parties agree on encryption methods and verify each other’s identities, the secure session is established, and data transfer can begin.

Principles of REST API

Statelessness: Each request from the client to server must contain all the information the server needs to fulfill the request.
Client-Server Architecture: Separation of concerns between client and server, enabling each to evolve independently.
Uniform Interface: A standardized interface between client and server, often using HTTP methods.
Layered System: A client cannot ordinarily tell whether it is connected directly to the end server or to an intermediary.

REST API Methods

GET: Retrieve data from the server. Example: GET /users retrieves a list of users.
POST: Submit data to the server to create a new resource. Example: POST /users with user data creates a new user.
PUT: Update an existing resource on the server. Example: PUT /users/1 updates the user with ID 1.
DELETE: Remove a resource from the server. Example: DELETE /users/1 deletes the user with ID 1.

DNS (Domain Name System) and Lookup Process

DNS

A system that translates human-readable domain names into IP addresses.

DNS Lookup Process

Query Initiation: A user types a domain name into the browser.
Recursive Resolver: The query is sent to a DNS resolver, which checks its cache.
Root Name Servers: If not cached, the resolver queries root servers to find the authoritative server for the domain.
TLD Name Servers: The resolver then queries the top-level domain (TLD) servers for the domain.
Authoritative Name Servers: Finally, the resolver queries the domain’s authoritative servers for the IP address.
Response: The IP address is returned to the resolver, which sends it back to the client.