Revisiting the "Rules of React"

Wed May 15 2024

React has become a cornerstone of modern web development, providing developers with a robust framework to build dynamic and interactive user interfaces. As the ecosystem evolves, so do the tools and best practices that ensure optimal performance and maintainability. One such development is the React Compiler, a powerful tool that can enhance your codebase with features like auto memorization. However, to fully leverage these enhancements, it's essential to adhere to the "Rules of React."

The Rules of React

The "Rules of React" are guidelines designed to help developers write predictable and efficient code. These rules ensure that components behave as expected and that the React Compiler can optimize your application effectively. Let's revisit these rules and explore why they are more critical now than ever.

1. Only Call Hooks at the Top Level

Hooks are a fundamental feature of React, allowing you to use state and other React features without writing a class. The first rule is to only call hooks at the top level of your function components. This means you should not call hooks inside loops, conditions, or nested functions.

Why it matters: Calling hooks conditionally or in nested structures can lead to unpredictable behavior and bugs. The React Compiler relies on the consistent order of hooks to maintain state correctly. By following this rule, you ensure that hooks are called in the same order every time a component renders, enabling the compiler to optimize your code.

2. Only Call Hooks from React Functions

Hooks should only be called from React function components or custom hooks. This rule ensures that hooks are used in the right context and helps maintain the predictable behavior of your components.

Why it matters: Calling hooks outside of React functions can break the rules of hooks and lead to errors. By adhering to this rule, you ensure that hooks are used appropriately, allowing the React Compiler to apply optimizations like auto memorization effectively.

3. Declare All Dependencies in useEffect

When using the useEffect hook, it's crucial to declare all dependencies that the effect depends on. This rule ensures that your effects run correctly and only when necessary.

Why it matters: Missing dependencies can lead to stale closures, where the effect uses outdated values. This can cause bugs and unexpected behavior. By declaring all dependencies, you help the React Compiler understand when to re-run effects, ensuring optimal performance and consistency.

4. Use Stable References for Dependencies

When passing dependencies to hooks like useEffect or useCallback, use stable references. This means using useMemo or useCallback to memoize functions or objects that are passed as dependencies.

Why it matters: Unstable references can cause hooks to re-run more often than necessary, leading to performance issues. By using stable references, you minimize unnecessary re-renders and side effects, allowing the React Compiler to optimize your application effectively.

The React Compiler and Auto Memorization

The React Compiler is an exciting development that brings automatic optimizations to your React codebase. One of its key features is auto memorization, which can significantly improve the performance of your application by automatically memoizing components and hooks. However, these optimizations are only possible if you follow the "Rules of React."

Auto Memorization Explained: Auto memorization helps reduce unnecessary re-renders by caching the results of expensive computations and returning the cached result when inputs have not changed. This can lead to substantial performance gains, especially in complex applications.

Leveraging Auto Memorization: To fully benefit from auto memorization, your code needs to be predictable and follow the rules outlined above. The React Compiler relies on these rules to identify opportunities for optimization. By adhering to the rules, you ensure that your code is in a state that the compiler can optimize effectively.


The "Rules of React" are more critical now than ever. With the advent of the React Compiler and its powerful features like auto memorization, following these rules ensures that your codebase is not only correct and maintainable but also optimized for performance. By revisiting and adhering to these rules, you can unlock the full potential of the React Compiler and build faster, more efficient applications.

For more detailed information on the "Rules of React," you can visit the official React documentation. To learn more about the React Compiler and its capabilities, check out the React Compiler documentation.

By embracing these best practices, you can stay ahead in the ever-evolving world of React development and deliver high-quality, performant applications to your users.

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