[Question] How to optimize React component rendering performance?

[mvproot]

Body

Hi everyone,

I'm working on a React application with a complex component hierarchy. I'm noticing that my component renders are slow and causing performance issues.

Specifically:

• I have a parent component with 50+ child components
• Each child component has its own state
• The parent updates frequently
• I'm using regular JavaScript functions for computations

I've tried basic optimizations but they don't seem to be enough.

What are the best practices for optimizing React component rendering? Should I use useMemo, useCallback, or React.memo? Any other suggestions?

Thanks in advance! 🙌

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[iamriskycahyan]

Hello! Dealing with a complex component hierarchy and performance issues is a very common challenge. Based on your scenario (frequent parent updates, 50+ children, and stateful children), the problem is likely unnecessary re-renders of your child components.

Here are the best practices, focusing on the tools you mentioned:

1. Primary Strategy: Prevent Unnecessary Renders
   The three tools you asked about work together to "memoize" and prevent updates when props haven't changed:

React.memo(): This is your highest priority. Apply this to all 50+ child components. It will prevent a child from re-rendering unless its specific props change.

useCallback(): Use this for any functions you pass as props to your React.memo() children. Without it, the function reference changes on every parent render, forcing the memoized child to re-render.

useMemo(): Use this to wrap your expensive JavaScript computations. It ensures the computation only re-runs when its specific dependencies change, not on every component render.

2. State Optimization
   State Colocation: Review your state. If a piece of state only affects a few children, move that state down to the closest common ancestor of those children. The less state you keep in the top-level parent, the fewer components will be forced to update when the parent re-renders.

3. Handling Large Lists
   Virtualization/Windowing: Since you have 50+ components, if they are rendered in a list, you should consider virtualization. This technique only renders the items currently visible in the user's viewport, drastically reducing the total number of components the browser has to manage. Libraries like react-window or react-virtualized can help here.

By strategically applying React.memo() and useCallback(), and managing your state more locally, you should see a massive improvement in performance! Good luck! 🙌