Optimizing React Performance: Preventing Unnecessary Re-renders
React 16 introduces a new feature that allows you to decide whether state gets updated via setState, preventing unnecessary DOM updates. In this article, we’ll explore how to use this feature to improve the performance of your React applications.
The Problem: Unnecessary Re-renders
When you update state in a React component, it triggers a re-render of the entire component tree. However, if the state doesn’t actually change, this re-render is unnecessary and can cause performance issues.
The Solution: Returning Null from setState
To prevent unnecessary re-renders, you can return null from setState if the state’s new value is the same as its existing value. This tells React not to update the state and trigger a re-render.
Example: Optimizing a Mocktail Selection App
Let’s take a look at an example app that demonstrates how to use this feature. We have a mocktail selection app that updates the selected mocktail when the user clicks on a button.
Before Optimization
Before optimization, the app unnecessarily re-renders the entire component tree every time the user clicks on a button, even if the selected mocktail doesn’t change.
After Optimization
After optimization, the app only re-renders the component tree when the selected mocktail actually changes. If the user clicks on the same button multiple times, the app doesn’t re-render the component tree.
Code Example
Here’s an example of how to optimize the updateMocktail method to return null from setState if the state’s new value is the same as its existing value:
updateMocktail = (newMocktail) => {
this.setState((prevState) => {
if (prevState.mocktail === newMocktail) {
return null;
}
return { mocktail: newMocktail };
});
};
Conclusion
By returning null from setState when the state’s new value is the same as its existing value, you can prevent unnecessary re-renders and improve the performance of your React applications. This technique is especially useful when working with complex component trees or when optimizing for performance-critical scenarios.