context setup react 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: context in react

// Context lets us pass a value deep into the component tree// without explicitly threading it through every component.// Create a context for the current theme (with "light" as the default).const ThemeContext = React.createContext('light');
class App extends React.Component {
  render() {
    // Use a Provider to pass the current theme to the tree below.    // Any component can read it, no matter how deep it is.    // In this example, we're passing "dark" as the current value.    return (
      <ThemeContext.Provider value="dark">        <Toolbar />
      </ThemeContext.Provider>
    );
  }
}

// A component in the middle doesn't have to// pass the theme down explicitly anymore.function Toolbar() {
  return (
    <div>
      <ThemedButton />
    </div>
  );
}

class ThemedButton extends React.Component {
  // Assign a contextType to read the current theme context.  // React will find the closest theme Provider above and use its value.  // In this example, the current theme is "dark".  static contextType = ThemeContext;
  render() {
    return <Button theme={this.context} />;  }
}