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The useContext hook in React
January 04, 2022
1 min

Table Of Contents

01
A classic use of Context
02
useContext solves nesting

React is the leading frontend framework. The team recently released a new way to write React components using a function instead of class. This new method allows developers to keep the ease of function and still have the deepness of React lifecycle by using hooks.

Let’s see how to use the useContext hook and why it’s better than the previous React Context API.

Context lets you pass data between components easily. For a simple app, Context can be enough to use instead of Redux, which adds a lot of complexity.

A classic use of Context

The classical way to use the Context component is to initiate the React Context, with createContext wrapping the component that needs the Context with the React Provider component, and then retrieve it in children or grandchildren by wrapping it with the React Consumer component.

Note that you need to use the value props inside the Provider to change the value of the React Context.

import React from "react";
import { render } from "react-dom";

const { Consumer, Provider } = React.createContext();

function App() {
  // Provider Make the data available to all children
  return (
    <Provider value={'Hello World'}>
      <div>
        <HelloWorld />
      </div>
    </Provider>
  );
}

function HelloWorld() {
  // Consumer allow to retrieve the data in children without props
  return (
    <Consumer>
      {value => <p> {value}.</p>}
    </Consumer>
  );
}

render(<App />, document.querySelector('#root'));

Example on CodeSandebox

useContext solves nesting

In the example, there is extra nesting due to how React Consumer works. useContext solves that issue. Let’s take the previous example and rewrite the HelloWorld function with useContext.

import React, {useEffect} from "react";

// Other way to define Context
const Context = React.createContext('Hello World');

function App() {
  // value not needed because defined on createContext
  return (
    <Provider>
      <div>
        <HelloWorld />
      </div>
    </Provider>
  );
}


function HelloWorld() {
  const value = useContext(Context);
  //const value = useContext(Consumer); also works when destructuring Context
  return <p>{value}</p>;
}

It’s easier to retrieve the value with useContext and avoid unnecessary nesting, and it keeps the code readable.

This example is easy, but sometimes you will need to retrieve multiple Contexts, which leads to numerous nesting. With useContext, it’s as easy as declaring a value.


Tags

javascriptreactjsreact-hooks

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