React’s built-in Context API code example

Example 1: reactjs context

==App.js========================================
import React from 'react';
import PageContextProvider from './PageContextProvider';
import Header from './Header';
function App() {
    return (
        <div className="App">
            <PageContextProvider>
                <Header />
            </PageContextProvider>
        </div>
    );
}
export default App;


==PageContextProvider.js=========================
import React, { useState, useEffect, createContext } from 'react';
export const PageContext = createContext();
const PageContextProvider = (props) => {
    const [user, setUser] = useState({
        'name': 'harry potter'
    });
    return (
        <PageContext.Provider value={{ 
            user: user,
        }}>
        	{props.children}
        </PageContext.Provider>
    );
}
export default PageContextProvider;


==Header.js=====================================
import React, { useContext } from 'react';
import { PageContext } from './PageContextProvider';
const Header = () => {
    const { user } = useContext(PageContext);
    return (
        <div className="header">
        	{user.name}
        </div>
    );
}
export default Header;

Example 2: react context api

DEFINITION::::::
Context provide a way to pass data through the component tree without 
having to pass down manually at every level

HOW TO USE::::::
DECLARATION:::
	const MyContext = React.createContext()
Creating a new Context for each unique piece of data that needs to be available
throughout your component data
	const LocaleContext = React.createContext()
Properties of LocaleContext --------
	LocaleContext.Provider
    LocaleContext.Consumer

What is a Provider 
	Allows us to "declare the data that we want available throughout our
	component tree"

What is a Consumer
	Allows "any component in the tree that needs that data to be able to 
    subscibe to it"

How to use Provider	
	<MyContext.Provider value={data}>
      <App />
    </MyContext.Provider>