React Training
  • React JS Library
  • Roadmap
  • Training OutLine
  • React js basics
    • Understanding React JS
    • React JS a framework?
    • Setting Up React
    • Say Hello to React
    • Everything is a Component
    • Create-react-app
  • React Building Blocks
    • JSX and Babel
    • One Way Data Flow
    • Virtual DOM
    • V of MVC
    • React Terminology
    • React Tooling
  • Day 01
    • Day 01 OutLine
    • All About JSX
    • React Tools/ npm & webpack
    • Introduction of Webpack
    • Hello world using webpack
      • Webpack Setting up with React
    • NPM Scripts | Package JSON
      • Package.json file
    • React JS Principles
      • One Way Data Flow
      • V of MVC
      • Virtual DOM
    • Create React App - Part-1
    • Create React App - Part-2
  • Day 02
    • Quick Recap
      • Quiz
    • State & Props
      • State & Props in Depth
      • State Vs Props | Compare
    • React LifeCycle Methods
      • React LifeCycle Methods for V-0.16 x
    • Constructor | Lifecycle
    • Write Flicker App | First App
  • Day 03
    • Quick Recap
    • Life Cycle Flow
      • Birth and Mounting
      • Initlization and Construction
      • Pre Mounting
      • Render Method
      • componentDidMount
    • Type of React Components
      • Examples- Quick Compare
      • Class and Functional components
      • Functional Components
    • YouTube application
      • Component Design
    • All in One LifeCycle
  • Assignment
    • React App development
  • Day 04
    • Quick Recap on Lifecycle
    • Lifecycle deprecated/New Methods
      • New Lifecycle Methods
    • Lets Build App Netflix | Mock
  • Assignment
    • Github battle App | Assignment
  • Day 05
    • Quick Recap : Hooks
    • ES6 Features | Hands-on
      • ES6 Code Examples
    • Next Stop - React Router | SPA
      • Code examples | Router
      • React Router Building Blocks
      • Application using react-router-dom
  • Day 06
    • Router V4 | Quick Recap
    • ES2015 | 16 Quick Recap
    • LifeCycle Methods -Part-1
    • LifeCycle Methods -Part-2
  • Day 07
    • Quick Recap | New Lifecycle
    • Quick Recap | React Routing
    • Context API | React JS
      • component with context APIs
      • Context API | examples
    • App using Hooks/Context APIs
  • Assignment
    • Assignments
  • State Management Day-08
    • Quick Recap
    • Managing React State
      • What is Redux
      • Understanding Redux
      • Hello World "Redux"
  • React Redux Day - 09
    • Redux State Manager
    • Redux Redux Development
    • Simple Application | Redux
  • Redux Live Application Day -10
    • Redux with existing Application
      • Redux with React App
      • Lets Build More Apps
      • Should I use Redux from Dan
    • Quick Look at JS in React
    • Learn By Reading
  • miscellaneous Items - Day 11
    • Hooks useReducer
    • Hooks useContext
    • Hooks useRef
    • Hooks useEffect
    • Hooks useState
    • Lazy Loading and code splitting
    • Styling React Component
  • React Next Step - Day 12
    • Topics
    • Jest and Enjyme Testing
    • Examples: Testing
  • React Native
    • What is React Native
    • Setting up Environment
      • Linux Systems
    • React Native Hello World App
    • React Native Architecture
    • React Native Vs Native
    • Expo Cli or React Native CLI
  • React Native core Fundamental
    • React Native "Hello World"
    • Course OutLine
    • Getting started with Expo App
    • Layout with Flexbox
    • Working with Styles and Events
    • Manging Component State and Props
    • Build Simple Task List Application
  • What to Debug & How to Debug
    • Debug React Native Application
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  1. Day 07

Context API | React JS

what is context API and why we need this

Recently React introduced some new cool fetures, one of interesting and much awaited feature is New Context API. New context API introduced with version 16.3. Context API’s are very useful in state management without props drilling. Let’s deep dive into the same.

Problem

In many cases, in our application we need to pass the state of componenet to two-three level deep. so we passed props down to the levels and levels of the component tree when not all of those components necessarily need those props. Suppose component hierarchy is complex then state management would be overhead for developers.

Solution

For state management theres are couple of libraries available like Redux (most used and trending). But React introduced the Context API to solve the problem of props drilling and made developers work of state management simple.

When to use Context

As React suggests “If you only want to avoid passing some props through many levels. Context is designed to share data that can be considered “global” for a tree of React components, such as the current authenticated user, theme, or preferred language.”

How to use Context

So now if you want to use context in your application, first create context object.

import { createContext } from 'react';
const {Provider, Consumer } = React.createContext();

Then create a wrapper component that will return Provider component and also add as children all the components from which you want to access the context.

class ProviderComponent extends Component {
    state = {
        title : “Vishal”,
    }
render() {
        return ( 
        <Provider value={this.state}>
          <Website />
        </Provider>
        )
    }
}

Our Website component look like

const Website = () => (
  <div>
    <Header />
    <Footer />
  </div>
)

Now if we want to access the title from provider component to the Header componet, we can simply consume state of provider component using context without prop drilling.

const Header = () => (
  <div>
     <Consumer>
        {(context) => context.title}
      </Consumer>
  </div>
)
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Last updated 5 years ago

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