The React Context API uses a Provider and Consumer pattern to share data throughout an application. The provider role is played by a React component that makes data available to its descendant components. When one of those descendants accesses the shared data, it becomes a consumer.

To use the React Context API, we start by creating a React context object, a named object created by the React.createContext() function.

const MyContext = React.createContext();

Context objects include a .Provider property that is a React component. It takes in a value prop to be stored in the context.

<MyContext.Provider value="Hello world!"> <ChildComponent /> </MyContext.Provider>

That value — in this case, the string "Hello world!" — is available to all its descendent components. Descendent components — in this case, ChildComponent — can then retrieve the context’s value with React’s useContext() hook.

import { useContext } from 'react'; import { MyContext } from './MyContext.js' const ChildComponent = () => { const value = useContext(MyContext); return <p>{value}</p>; } // Renders <p>Hello, world!</p>

The useContext() hook accepts the context object as an argument and returns the current value of the context. Rejoice — prop drilling that value is no longer needed!

Note: If a component attempts to use a context that isn’t provided by one of its ancestors, useContext() will return null.

Note: In some older React applications, you might instead see SomeContext.Consumer used to subscribe to a Context. That alternative is generally considered bad practice and avoided for being overly verbose and difficult to work with.



In the workspace’s ThemeContext.js file, use React.createContext() to create a new context. Then, store the new context in a variable named ThemeContext. Finally, export ThemeContext as a named export.


Now that you’ve created a ThemeContext, import it into the ContactsApp.js file. In the ContactsApp function component, wrap the existing returned children inside a <ThemeContext.Provider> component with a value prop set to "light".


You’ve successfully set up the ThemeContext object’s .Provider property to be used by the ContactsApp component to provide the "light" value to all its descendants. Let’s use that value in the ContactItem component instead of the drilled theme prop.

In the ContactItem.js file, remove the theme prop from the ContactItem component’s prop list. Have it use React’s useContext() hook to retrieve the ThemeContext’s provided theme value instead.


Now that ContactItem can retrieve the theme using useContext(), its parent component ContactList doesn’t need to prop drill the theme prop.

In ContactsList.js, remove the unused prop drilling.


Now that ContactsList components don’t need to prop drill a theme prop, its parent component ContactsSection doesn’t need to prop drill the theme prop either.

In ContactsSection.js, remove the unused prop drilling.


And finally, now that ContactsSection components don’t need to prop drill a theme prop, its parent component ContactsApp doesn’t need to prop drill the theme prop either.

In ContactsApp.js, remove the unused prop drilling.

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