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bilel salem
bilel salem

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Mastering React: A Deep Dive into Memoization and Component Optimization

Hello Everyone, السلام عليكم و رحمة الله و بركاته,

As mentioned Before, we will go through each note in the article "Advanced React Insights: Deep Dive into Key Concepts" and provide detailed explanations and an in-depth analysis.

Memoization and Component Optimization: General Concepts


Memoization is an optimization technique used to improve the efficiency of functions by caching their previously computed results. When a function is called with the same arguments, memoization allows the program to return the cached result instead of recomputing it.

Key Points:

  1. Cache Storage: Memoization involves storing the results of expensive function calls and reusing those results when the same inputs occur again.
  2. Pure Functions: Memoization is most effective with pure functions—functions that always produce the same output for the same input and have no side effects.
  3. Performance Improvement: By avoiding repeated calculations, memoization can significantly improve the performance of applications, especially those with heavy computations or recursive function calls.
  4. Implementation: Memoization can be implemented manually using data structures like dictionaries or via built-in language features and libraries (e.g., functools.lru_cache in Python).

Component Optimization

Component optimization focuses on improving the performance of software components, especially in the context of UI frameworks. The goal is to reduce unnecessary re-renders and improve responsiveness.

Key Strategies:

  1. Shallow Comparisons: Implement shallow comparisons to determine if a component’s props or state have changed, thus deciding if a re-render is necessary.
  2. Pure Components: Use pure components that implement a shallow comparison of props and state to prevent unnecessary renders.
  3. Memoization of Components: Memoize components to avoid re-rendering unless their inputs (props or state) change.
  4. Virtualization: Virtualize large lists or grids to render only the visible items, reducing the rendering load.
  5. Debouncing and Throttling: Control the rate of state updates and re-renders to prevent performance bottlenecks.

Memoization and Component Optimization in React

Memoization in React

In React, memoization is used to optimize the performance of functional components and hooks. React provides several built-in hooks and higher-order components (HOCs) to facilitate memoization.

Key Techniques:

  1. React.memo:
    • A higher-order component that memoizes the result of a functional component.
    • Only re-renders the component if its props have changed.
   const MyComponent = React.memo((props) => {
       /* render logic */
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  1. useMemo:
    • Memoizes the result of a calculation within a functional component.
    • Useful for expensive calculations that shouldn’t be re-executed on every render.
   const memoizedValue = useMemo(() => computeExpensiveValue(a, b), [a, b]);
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  1. useCallback:
    • Memoizes a function definition so that it doesn’t get recreated on every render.
    • Essential when passing callback functions to child components to prevent unnecessary re-renders.
   const memoizedCallback = useCallback(() => {
       doSomething(a, b);
   }, [a, b]);
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Advanced Concepts in React Component Optimization

  1. Custom Hooks for Optimization:
    • Custom hooks can be created to encapsulate optimization logic, making it reusable across different components.
   const useOptimizedValue = (computeFn, deps) => {
       return useMemo(computeFn, deps);
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  1. React Profiler:
    • Use the React Profiler to identify performance bottlenecks in your application.
    • Helps in understanding which components are rendering too frequently and why.
   <React.Profiler id="MyComponent" onRender={callback}>
       <MyComponent />
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  1. Code Splitting and Lazy Loading:
    • Dynamically load components only when they are needed using React’s lazy and Suspense.
    • Reduces the initial load time and improves perceived performance.
   const LazyComponent = React.lazy(() => import('./LazyComponent'));
   <Suspense fallback={<div>Loading...</div>}>
       <LazyComponent />
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  1. Context Optimization:
    • Avoid passing down large contexts that cause widespread re-renders.
    • Use selectors and specialized context providers to minimize re-renders.
   const OptimizedContext = React.createContext();
   const OptimizedProvider = ({ children }) => {
       const [state, setState] = useState(initialState);
       const value = useMemo(() => ({ state, setState }), [state]);
       return (
           <OptimizedContext.Provider value={value}>
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  1. Reselect and Selector Libraries:
    • Use selector libraries like Reselect to create memoized selectors for state management libraries (e.g., Redux).
    • Ensures that derived data is only recomputed when necessary.
   import { createSelector } from 'reselect';

   const selectItems = state => state.items;
   const selectFilteredItems = createSelector(
       items => items.filter(item =>
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By employing these advanced techniques, we can create highly performant React applications that efficiently manage rendering, state updates, and overall application responsiveness.

Top comments (13)

lgtome profile image

Maybe good to know that React.memo can have a second argument function that can equal props and you can manipulate it.

bilelsalemdev profile image
bilel salem

Thank you for the Information

miguelrodriguezp99 profile image

thank you very much for the information

lotfijb profile image
Lotfi Jebali

Insightful, keep it up !

vkpdeveloper profile image
Vaibhav Pathak

These articles doesn't make any sense now, just use React Compiler and you don't need to memoize yourself.

brense profile image
Rense Bakker

React compiler is a bandaid for a problem that only exists because there's a split in the React community between people who think its not necessary to prevent excessive rerenders and people who figured out how problematic that is. I think it's still very useful to understand why memorization is needed because it helps to understand what React compiler does. It's also not just a React problem, shallow comparison issues pop up everywhere. Understanding the difference between values and references is essential knowledge for a good developer.

vkpdeveloper profile image
Vaibhav Pathak

I think people needs to understand more about the memory consumption then just knowing what's useMemo, the problem is when they get to know useMemo, people just start using it all the places. Even if it doesn't make any sense, the same problem I see with React Compiler, they make some decisions but still they are literally doing memorization everywhere, which is not really a good or even required.

The first thought that comes to mind when you just know what useMemo does is wherever you see performance issue, you are like just use useMemo.

That's really bad.

Thread Thread
brense profile image
Rense Bakker

Performance issues is probably the last place where you should useMemo because it wil hide the actual problem. I'm more concerned with triggering renders where the state hasn't fully propagated because the reference to a state object got destroyed, which can cause weird behavior in the app and in worst case it can cause an infinite loop that blocks the cpu thread. Thats why I recommend to memoize everything thats not a string, number or boolean. You won't know 3 months from now when you're making a new component and passing props down, which ones are properly memoized and which aren't. Because react compiler intends to make you forget about any kind of memorization, this is the same strategy they employ. Memoize everything.

bilelsalemdev profile image
bilel salem

Comapnies don't use React 19 until it will be Stable

chafroudtarek profile image
Chafroud Tarek

Very helpful man 💯

adem_bc profile image

Great Job

thunder6230 profile image

With react 19 all has gone 🙂

faroukabichou profile image
Farouk Abichou

Great Job bilel

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