React’s Strict Mode is a powerful tool that helps developers write more resilient applications. By highlighting potential problems in the application, it encourages best practices and promotes better code quality. In this post, we’ll explore what Strict Mode is, its benefits, how to implement it in your React application, and some common pitfalls to watch out for.

What is React’s Strict Mode?

Strict Mode is a feature in React that activates additional checks and warnings for its descendants. It’s a tool for identifying potential issues in an application and is especially useful during the development phase.

Some of the benefits of using strict mode are:

1. Identifies Unsafe Lifecycles: It helps detect components that are using deprecated lifecycle methods that can lead to bugs.
2. Warning About Legacy String Refs: Strict Mode will warn you if you’re using legacy string refs, encouraging the use of callback refs instead.
3. Detects Unexpected Side Effects: It runs components twice in development mode to help identify side effects and ensure that the state updates are predictable.
4. Improves Component Reusability: By enforcing best practices, it encourages developers to write more modular and reusable components.

How to Implement Strict Mode

Implementing Strict Mode in your React application is straightforward. Wrap your application or specific components with <React.StrictMode>.

import React from 'react';
import ReactDOM from 'react-dom';
import App from './App';

ReactDOM.render(
  <React.StrictMode>
    <App />
  </React.StrictMode>,
  document.getElementById('root')
);

In this example, App and all its child components will be subjected to the checks provided by Strict Mode.

Common Pitfalls When Using Strict Mode

1. Double Rendering in Development: Be aware that components may render twice in development mode, which can be confusing. This is done to identify side effects and ensure your components behave as expected.
2. Compatibility with Third-Party Libraries: Some third-party libraries may not be compatible with Strict Mode. If you encounter issues, check the library’s documentation or consider alternatives.

Conclusion

React’s Strict Mode is a valuable tool for enhancing application reliability and performance. By implementing it in your projects, you can catch potential issues early, promote best practices, and ultimately build a more robust React application. Nowadays we have tools (like CRA or Vite) that scaffold the code and this feature is added by default and don’t have to worry about it. But hopefully with this posts you can have a clearer idea of what strict mode is about and how it works.

So the next time you go to a YouTube tutorial and ask you to “clean” the code by removing “unnecessary” things, you better think it twice before doing it and decide by yourself it it’s safe or not.