Programs

React useLayoutEffect() Explained

Introduction

ReactJS is a JavaScript library for building user interfaces. It enables developers to develop reusable UI components and efficiently manage the state of those components.

The purpose of useLayoutEffect() in React is to perform side effects that require access to the DOM and should be executed synchronously before the browser paints, allowing for layout-related calculations and immediate visual updates. 

Read on to learn more about the useLayoutEffect() method in React in this blog, and check out the Full Stack Software Development Bootcamp from upGrad.

Understanding the Difference Between useEffect and useLayoutEffect

useEffect useLayoutEffect
useEffect runs after the browser has painted, allowing for smoother rendering and better performance.  useLayoutEffect runs before the browser paints, potentially blocking rendering and leading to a less smooth user experience.
It is asynchronous, meaning it defers its execution until after the browser has painted. It is synchronous, and its effects are applied immediately, potentially blocking rendering.
It does not impact the rendering process, as it runs asynchronously. It can block rendering if it performs time-consuming tasks or modifies the DOM layout.
It is suitable for side effects that don’t require synchronous updates or direct interaction with the DOM layout. It is helpful for side effects that rely on or interact with the DOM layout, as it runs before the browser paints.
useEffect is recommended for most cases due to its asynchronous nature, which helps avoid blocking rendering. useLayoutEffect should be used cautiously, as it can cause performance issues if not used carefully, especially when performing expensive operations or DOM mutations.

It’s important to choose the appropriate hook based on the specific requirements of your application to ensure optimal performance and user experience.

When To Use useLayoutEffect in React

Here are some scenarios where you might consider using useLayoutEffect:

  • Updating DOM layout: You might need to update the DOM immediately after a component has been rendered. You might also want to ensure that the updated layout is reflected before the browser paints. For these purposes, you can use useLayoutEffect. For instance, you might want to measure the dimensions of an element or calculate its position relative to other elements.
  • Synchronising animations: You might have complex animations or transitions that depend on the layout of the components. For this, useLayoutEffect can help ensure that the necessary DOM changes are applied synchronously before the next frame is painted. This can help prevent visual glitches or inconsistencies in the animation.
  • Performing imperative DOM operations: In certain cases, you might need to perform imperative DOM operations, such as scrolling to a specific element, focusing on input, or updating the DOM based on user interactions. useLayoutEffect can be useful in these situations to ensure that the DOM is updated synchronously, providing a consistent and expected behaviour.

Check out our free technology courses to get an edge over the competition.

Syntax of useLayoutEffect Hook

The useLayoutEffect hook in React takes two arguments: a callback function and a dependency array. 

Step 1: Import the useLayoutEffect hook from the ‘react’ module:

Step 2: Use the useLayoutEffect hook in your component function:

Inside the useLayoutEffect callback function, you can perform side effects, such as updating the DOM, measuring dimensions, or any other imperative operations that rely on the layout. This function will be executed synchronously before the browser paints.

Optionally, you can return a cleanup function from the useLayoutEffect callback. This cleanup function will be invoked when the component is unmounted or the dependencies in the dependency array change. This is useful for cleaning up any resources or subscriptions created within the effect.

The dependency array is an optional argument. It allows you to specify dependencies the useLayoutEffect hook should watch for changes. When any dependencies change, the effect will be re-evaluated, and the callback function will be called again. If the dependency array is empty, the effect will only run once.

Check Out upGrad’s Software Development Courses to upskill yourself.

How To Use useLayoutEffect With an Example

Here is a useLayoutEffect example to update the width state whenever the window is resized. The width state is initially set with the current window width and is updated whenever the resize event occurs:

Step 1: Import the necessary React hooks:

Step 2: Create a functional component ExampleComponent:

Step 3: Use useLayoutEffect to perform the necessary DOM measurement and updates:

Inside the useLayoutEffect callback, we define the handleResize function to update the width state whenever the window is resized. We then add the event listener for the resize event and perform the initial measurement to set the initial width.

The cleanup function is returned from the useLayoutEffect callback, removing the event listener when the component is unmounted or the dependencies change. In this case, the dependency array is empty, indicating that the effect should only run once.

Step 4: Render the component and display the width state:

Finally, we render the component and display the width state value in a paragraph element.

With this example, the component will update the width state whenever the window is resized, providing a real-time display of the window width. You can explore this topic better with a Master of Science in Computer Science from LJMU

Managing Component State With useLayoutEffect

Here is an example that demonstrates managing component state with useLayoutEffect. We have a component ExampleComponent that increments the count state after a delay of 3 seconds using useLayoutEffect. Note that in most cases, it’s more appropriate to use useEffect for this kind of asynchronous state update, but we’re using useLayoutEffect here to demonstrate its usage in managing component state:

Step 1: Import the necessary React hooks:

Step 2: Create a functional component ExampleComponent:

Step 3: Use useLayoutEffect to manage the state update:

Inside the useLayoutEffect callback, we set up a timeout using setTimeout to update the count state after 3 seconds. The dependency array contains the count, which means the effect will be re-evaluated, and the callback will be executed whenever the count changes.

The cleanup function returned from useLayoutEffect clears the timeout to prevent any potential memory leaks or unwanted state updates when the component is unmounted or when the count dependency changes.

Step 4: Render the component and display the count state:

Finally, we render the component and display the count state value in a paragraph element.

Explore Our Software Development Free Courses

Updating the DOM With useLayoutEffect

To update the DOM using useLayoutEffect, you can perform DOM manipulations directly within the effect’s callback function. Since useLayoutEffect runs synchronously before the browser paints, any DOM changes in the effect will be reflected before the next frame is rendered.

Here’s an example that demonstrates updating the DOM with useLayoutEffect. We use useLayoutEffect to update the background colour and text colour of an <div> element. We access the DOM element using a useRef hook and perform the DOM manipulations inside the effect’s callback.

Step 1: Import the necessary React hooks:

Step 2: Create a functional component ExampleComponent:

Step 3: Use useLayoutEffect to update the DOM:

Inside the useLayoutEffect callback, we access the DOM element by accessing the current property of the elementRef object. Then, we update the background colour to blue and the text colour to white using the element’s style property.

The dependency array is empty, indicating that the effect should only run once after the initial render.

Step 4: Render the component and attach the ref to the <div> element:

Finally, we render the component and attach the elementRef to the <div> element using the ref prop.

As a result, the background colour of the <div> element will be updated to blue, and the text colour will be changed to white as soon as the component is rendered.

Tips and Tricks for Using useLayoutEffect

Here are some tips and tricks for using useLayoutEffect effectively in React:

  • Use it sparingly: useLayoutEffect runs synchronously and can potentially block rendering, so only use it when necessary for DOM-related layout effects.
  • Optimise performance: Ensure that the code inside useLayoutEffect is efficient and doesn’t introduce unnecessary delays.
  • Avoid circular dependencies: Be mindful of dependencies in the dependency array to prevent infinite loops.
  • Leverage clean-up: Use the optional clean-up function to unsubscribe from events or release resources.

In-Demand Software Development Skills

Common Mistakes To Avoid With useLayoutEffect

Here are common mistakes to avoid when using useLayoutEffect in React:

  • Overusing useLayoutEffect: Only use it when necessary for DOM-related layout effects to prevent unnecessary rendering delays.
  • Infinite loops: Ensure the dependency array is properly configured to avoid circular dependencies that cause infinite re-rendering.
  • Blocking the rendering pipeline: Avoid long-running synchronous operations or heavy DOM manipulations within useLayoutEffect to prevent blocking rendering.
  • Using it instead of useEffect: Use useEffect unless there’s a specific need for synchronous updates, as useLayoutEffect can have unintended side effects.

Conclusion

useLayoutEffect() is thus used for performing DOM measurements or imperative interactions immediately after React updates the DOM. It is essential for timing and layout-related operations. If you want to be an expert in React, among other software and web development aspects, enrol in an Executive PG Programme in Full Stack Development from IIITB by upGrad. This program delves deep into back-end and front-end development concepts. Enquire today to know more!

Frequently Asked Questions

Can useLayoutEffect cause performance issues?

If used improperly, useLayoutEffect can block rendering and cause performance issues. It's important to optimise the code inside useLayoutEffect and ensure it doesn't introduce unnecessary delays or heavy computations.

Are there any differences in usage between useLayoutEffect and useEffect?

No, the usage of useLayoutEffect is identical to useEffect. They both take a callback function and an optional dependency array. However, useLayoutEffect runs synchronously, and useEffect runs asynchronously.

Is it safe to use useLayoutEffect with server-side rendering (SSR)?

Using useLayoutEffect with server-side rendering can cause warnings or errors since it expects synchronous execution. In SSR, it's recommended to use useEffect instead to ensure consistent behaviour between the server and client.

Want to share this article?

Leave a comment

Your email address will not be published. Required fields are marked *

Our Popular Software Engineering Courses

Get Free Consultation

Leave a comment

Your email address will not be published. Required fields are marked *

×
Get Free career counselling from upGrad experts!
Book a session with an industry professional today!
No Thanks
Let's do it
Get Free career counselling from upGrad experts!
Book a Session with an industry professional today!
Let's do it
No Thanks