Mastering React Hooks: A Beginner’s Guide to useInsertionEffect

🤩 Promo

Have you ever faced situations where styles flicker or seem delayed due to dynamic updates? Enter React’s useInsertionEffect! This specialised hook ensures that CSS or style-related side effects are applied at just the right moment in the render cycle. Let’s dive deeper into how it works.

≏ Hook Definition

useInsertionEffect is a React Hook designed for low-level manipulation, specifically for injecting styles or managing side effects during the rendering phase, before the DOM updates.

⚙️ How Does It Work?

Unlike useEffect or useLayoutEffect, useInsertionEffect runs synchronously during the render phase, just before mutations are applied to the DOM. This makes it ideal for injecting dynamic styles or resetting certain styles that need to be present before the browser paints the UI.

Here’s a practical example:

import React, { useInsertionEffect, useState } from "react";

function DynamicStyler() {
  const [themeColor, setThemeColor] = useState("blue");

  useInsertionEffect(() => {
    const styleTag = document.createElement("style");
    styleTag.textContent = `
      .dynamic-theme {
        color: ${themeColor};
      }
    `;
    document.head.appendChild(styleTag);

    return () => {
      document.head.removeChild(styleTag); // Clean up
    };
  }, [themeColor]);

  return (
    <div>
      <h1 className="dynamic-theme">Dynamic Styling with useInsertionEffect</h1>
      <button onClick={() => setThemeColor("red")}>Change to Red</button>
      <button onClick={() => setThemeColor("green")}>Change to Green</button>
    </div>
  );
}        

👾 Good and Bad Practices

✅ Good Practices

• Use useInsertionEffect for injecting dynamic CSS, especially when working with styled-components or emotion.
• Always ensure cleanup logic is implemented to prevent memory leaks.

❌ Bad Practices

• Avoid using it for general-purpose effects; this hook is specifically for low-level styling.
• Do not use it in environments where server-side rendering (SSR) is required, as it doesn’t run on the server.

😌 When and Why We Need It

useInsertionEffect is most useful when you’re working with CSS-in-JS libraries like emotion or styled-components, or when dynamic styles are critical to the first paint of your application. This ensures that styles are in place before any visible UI updates occur, avoiding visual inconsistencies.

🧠 Key Points to Remember

1. It runs synchronously before DOM mutations, making it ideal for style-related side effects.
2. It does not replace useEffect or useLayoutEffect; use it for styling-specific use cases.
3. Be cautious about using this in non-browser environments, as it’s tied closely to the DOM.

😎 Tip

Combine useInsertionEffect with CSS-in-JS libraries to optimize your style injection and ensure flicker-free UI rendering.

🎬 Conclusion

useInsertionEffect is a powerful yet niche tool for React developers. While you might not need it in every project, it can be a game-changer for applications that rely heavily on dynamic or conditional styling.

📚 Summary

React’s useInsertionEffect ensures that styles or side effects critical to the UI are applied synchronously before the DOM is updated. While it’s a specialized hook, it shines in projects where precise control over style injection is required.

🤔 What Next

We’ve learned how to inject styles dynamically, but what if we want to manage asynchronous data updates and subscriptions? Guess the next hook! if yes let me know in the comments 🤗.