It is simple javascript functions that accept properties(props) in function and return HTML(JSX). It doesn’t have any state and lifecycle.

So, functional components are very simple but not powerful. But after React 16.8 version Functional components comes up with a new concept of Hooks, this makes it as powerful as Class by putting state and lifecycle through hooks.

Hooks:

State Hook

With state hooks now we can maintain the state of components.

State vs variable: Page doesn’t rerender when variable updated but render when state updated

useState:


Components are the building block of React Js. It is like bricks of building, custom Elements(like div, span) of HTML with content(return), behaviour(methods), data(fields).

Components can be of 2 types

  1. Class component: It is a class of Object orient programming. It has its own state and lifecycle. It must have render() method returning HTML.
  2. Functional component: It is simple javascript functions that accept properties(props) in function and return HTML(JSX). It doesn’t have any state and lifecycle. In our previous example, we have used only functional components.

Class component:

1.1. Basic Class structure:

import { Component } from “react”;class Header extends Component…

Basic Folder structure

  1. assets: for css,images etc
  2. components: common components like button,table
  3. core: core components like layout,headers, routing etc
  4. pages: independent pages for each url and its child components
  5. utils: constants, common util classes

React.JS History

React.JS was first used in 2011 for Facebook’s Newsfeed feature. Initial Release to the Public (V0.3.0) was in July 2013.

What is React.js?

React.js is an open-source JavaScript library that is used for building user interfaces specifically for single-page applications.

Single-Page Application

A single-page application is an app that works inside a browser and does not require page reloading during use.

most resources (HTML+CSS+Scripts) are only loaded once throughout the lifespan of application. Only data is transmitted back and forth.

Benefits of ReactJs

  1. It is fast as it is Single-Page Application
  2. It is fast as it uses Virtual DOM
  3. It is reusable because…

Features of Blockchain

· Distributed

Blockchain is built on Distributed Ledger and due to this the databases shared between all parties in a networks cross geography & regulatory boundary. Information can be quickly accessed by any parties without any manual intervention. All parties are directly connected through a highly transparent, secure, tamper-proof network so, no need for third parties.

· Immutable

Blockchain put each transaction in immutable block, and according to this the current state are calculated. once the transaction blocks get added on each ledger, no one can just go back and change it.

· Enhanced Security

Due to use of cryptography…


As a developer, we often face CORS issue in browser. From the Postman the API looks working but with the browser, we get the error message like this :

There is often debate between Front End and Backend team; ”the issue is from your side! we can show its working in Postman/Swagger ”.


Methods of REST service are like the verb in the sentence. They describe the actions that the service is performing on the given resource; like getting some car details,deleting user, updating account balance etc.

There is 5 Methods available in REST.

  1. GET
  2. POST
  3. PUT
  4. PATCH
  5. DELETE

GET

Get method is use to fetch resource data without making any changes of resource. GET request contain resource URL and method name only(no body param). All the required parameters should be sent via path param or Query pram.

When to use Path variable and when to use query param?
If you want to identify any resource/resources (by using id) you need to use path variable and if you want add filtering criteria like sorting it would be better to use query parameter.


Apache kafka is use for communication of multiple application. It use as a real-time data storage. Kafka is a publisher-subscriber message queue(MQ) which is use to pass data/message on a topic from publisher to subscribers.

Topic:

each message belongs to a particulate topic. Topic is similar to Table in DB and message/data is a row of that table.

Partitions:

Each topic is split into multiple parts known as partition. while creating a topic, we need to specify the number of partitions(the number is arbitrary and can be changed later). Each message gets stored into partitions with an incremental id known as its Offset value.

Brokers

A Kafka cluster is comprised of one or more servers which are known as brokers or Kafka brokers. Although a broker does not contain whole data, but each broker in the cluster knows about all other brokers, partitions as well as topics.


Client Side Technology

In server driven UI like jsp,jsf,php the code execute like validation,buisiness logic implementation, data binding is done in server end (except js code) and then the executed code is sent to client/browser(where the rendering done by client/browser).

But in case of Client driven UI the code base stored in server and the servers job is to send these files up to the client when they are needed. The code is then executes in client(browser) and when need to communicate with back-end using REST API the browser send the HTTP request to back-end server.

Development and Execution environment


Resources

The fundamental concept in any RESTful API is the resource. A resource is an object with a type, associated data, relationships to other resources, and a set of methods that operate on it.Under REST principles, a URL identifies a resource and method identifies actions on resource.

Resources can be grouped into collections. Each collection is homogeneous so that it contains only one type of resource, and unordered. Resources can also exist outside any collection. In this case, we refer to these resources as singleton resources. Collections are themselves resources as well.

URLs should include nouns, not verbs.

RESTful URI should refer to a resource that is…

Jyoti Karmakar

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