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HomeBlogWeb DevelopmentReact useLayoutEffect() - Hook API Reference In React
React is a robust and high-growing JavaScript library renowned in the web development industry. Due to its simplicity and data-fetching capabilities, React is now an ideal choice for building interactive, modern real-world applications. Hooks, the newly added feature in React V16.7, provides additional perks like adding hot reloading and using functional components effortlessly.
Hooks are functions that allow you to leverage state and many other React capabilities without writing ES6 class components. The useLayoutEffect Hook works in the same way as the useEffect Hook. In this tutorial, we’ll discuss the hook API reference with the help of the useLayoutEffect example. Before we begin further, check out the best pay after placement Full Stack Developer course.
Let’s Start!
Let’s Start!
A useLayoutEffect hook is a React hook that can be passed through in a component's render method to cause the react library to consider the page’s layout and change its calculations for things like spacing and overflow.
It is called synchronously once React all DOM modifications. It can be beneficial if you need to take DOM measures (such as the scroll positions or other styles for an element) and then make DOM changes a synchronous re-render by modifying the state. It works on the same principle as componentDidMount and componentDidUpdate in scheduling. Your function executing the DOM gets limited even before the browser has an opportunity to "paint" those adjustments; the user doesn't notice the changes the browser has repainted. If you are interested in exploring React hooks in-depth, we encourage you to sign up for ReactJS online training and upskill yourself.
useLayoutEffect()
The React useLayoutEffect hook takes two arguments. The first argument is a function called effect, and the second argument is an array of dependents. Generally, the first argument, effect, is either undefined or yields a cleanup function. The useLayoutEffect function signature is seen in the code below:
import React, { useLayoutEffect } from "react";
const APP = props => {
useLayoutEffect(() => {
//Do something and either return undefined or a cleanup function
return () => {
//Do some cleanup here
};
}, [dependencies]);
}; Both useEffect and useLayoutEffect take an effect function and an array of dependencies as arguments and return either an unknown or a cleanup function, as shown in the above function signature.
A side effect hook in React is an idea to create a theme that allows you to pass an anonymous function as an argument in React. It is a powerful tool that lets you break apart large pieces of code into smaller chunks. It enables us to encapsulate logic and functions without needing them all clumped together in other application parts.
Side Effect hooks are effective for writing modular code in React. It enables you to execute logic without needing it all clumped together. This means you can move smaller chunks of code around your app without breaking anything else. The functionalities are independent of other app parts and, thus, easier to maintain and reason about. It's a handy pattern for writing dynamic UIs, particularly for people who love working with data streams.
Anything that affects something outside the scope of the currently operating function is referred to as a side effect. We use this Hook to inform the component to perform some logic after rendering. The process supplied to the "useEffect" initial rendering and re-rendering of the element is defined inside the part, allowing the variables and functions defined inside the component to be accessed directly.
It uses the Closure concept to give users access to local operations and parameters declared within a process. It executes by default during the component's first rendering and re-rendering. After each call to render, React runs the Hook associated with the element.
useEffect and useLayoutEffect are the most widely used hooks in React. Both share similar function signatures, meaning the API exposed to the developers will be identical, regardless of your choice.
It is what you want to utilize 99 percent of the time. You'll likely migrate any code from componentDidMount, componentDidUpdate, and the component will unmount to useEffect once hooks are stable and you modify any of your class components to use hooks. The only caveat is that this occurs after reacting to your component, ensuring that your effect callback does not prevent the browser from painting. In contrast, componentDidMount and componentDidUpdate run synchronously after rendering in-class components. It's more efficient this way, and that's what you want.
Avoid useEffect if your effect is changing the DOM (through a DOM node ref), and the DOM modification will affect the layout of the DOM node between the time it is rendered and the time your effect mutates it. Instead, consider the React use layout effect hook. Otherwise, the user may see a flicker when your DOM mutations take effect—interested in learning web development? Enroll in basic Web Development course.
Deciding which hook to choose between useEffect and useLayouteffect may be tricky, so specifying your needs is the key. If your project involves animation or altering the DOM, prefer React use LayoutEffect instead of useEffect because only after the screen has been painted the useEffect Hook is called. If the DOM is mutated again right after the screen is painted, the result will be a flickering impact if the modification is apparent to the client. The useLayoutEffect hook, on the other hand, is called after the DOM has been changed but before the screen is painted. It is possible to avoid the unpleasant behavior mentioned above with the useEffect hook to alter the DOM right after painting the screen.
Consider the following scenario:
const ref = React.useRef()
React.useEffect(() => {
ref.current = 'some value'
})
// then, elsewhere in that hook or something, later
React.useLayoutEffect(() => {
console.log(ref.current) // <-- this logs an old value because this runs first!
})So, in situations like that, the solution is useLayoutEffect.
The uselayouteffect hook is a powerful React component that gives you the power to control where the input focus will go when rendering. This functionality can be used to implement any number of interactions with your users, from hiding content to designing a dropdown menu. It provides an alternative for the PureRenderMixin and allows you to fully customize what happens under the hood with just one line of code.
The critical distinction between useEffect and useLayoutEffect is when fired; however, it's difficult to quantify this difference without looking at real examples. In this part, I'll give three examples to show how the distinctions between useEffect and useLayoutEffect are significant.
Let's Simple counter application using useEffect that increments the count on a button click and prints the value using the effect hook in the console.
function App(){
const [count, setCount] = React.useState('0')
React.useEffect(() => {
console.log(count)
}, [count])
return(
<div>
<h1>The count is {count} </h1>
<button onClick={() => setCount(count + 1)}></button
</div>
)
}Let’s replace the useEffect hook with useLayoutEffect as highlighted:
function App(){
const [count, setCount] = React.useState('0')
React.useLayoutEffect(() => {
console.log(count)
}, [count])
return(
<div>
<h1>The count is {count} </h1>
<button onClick={() => setCount(count + 1)}></button
</div>
)
}You will observe that the app works the same, even after changing the hook. This validates the fact we have discussed earlier; both the hooks have identical function signatures. An important point to note here is that the output returned is either a cleanup function or an undefined value similar to the useEffect hook:
useLayoutEffect(() => {
// run effect here
}, [<dependency array>])However, after the firing order differentiates useLayoutEffect from useEffect hook. In the useEffect example discussed above, here's how React renders the function and handles interactivity:
In a nutshell, a useEffect hook only gets triggered only when DOM completes painting the screen. This way, it is asynchronous and prevents blocking the DOM manipulation on the net.
On the contrary, a useLayouteffect hook doesn’t care about DOM to complete painting the screen. That means it gets triggered synchronously, regardless of whether the DOM has been painted or not.
In our above discussion, we have seen that useLayoutEffect doesn't wait for DOM to paint the screen and gets fired right away. As a result, there is a great impact on the order of execution:
useEffect(() => {
console.log("USE EFFECT FIRST FUNCTION TRIGGERED")
}, [])
useEffect(() => {
console.log("USE EFFECT SECOND FUNCTION TRIGGERED")
}, [])You’ll see the output:
OUTPUT USE EFFECT FIRST FUNCTION TRIGGERED USE EFFECT SECOND FUNCTION TRIGGERED
This is no surprise while working with useEffect because it executes in the order sequentially as described in the code block. Note that depending on which effect function is triggered, different texts are logged, and as intended, the first impact mechanism is prompted before the second. When a component has much more than one useEffect call, the order of the impact calls is preserved. The first is produced, followed by the second, and so on. What happens if you replace the double useEffect hook with a useLayoutEffect Hook?
Let’s move forward and replace the second hook with a useLayoutEffect :
useEffect(() => {
console.log("USE EFFECT FUNCTION TRIGGERED")
}, [])
useLayoutEffect(() => {
console.log("USE EFFECT SECOND FUNCTION TRIGGERED")
}, [])You’ll see the output:
OUTPUT USE EFFECT SECOND FUNCTION TRIGGERED USE EFFECT FIRST FUNCTION TRIGGERED
You’ll notice that the useLayoutEffect gets executed before the useEffect hook without much concern for DOM mutation. Even though the React hook useLayoutEffect is set after the useEffect Hook, it gets triggered first! Before the DOM modifications are painted, the useLayoutEffect method is called synchronously. The useEffect function, on the other hand, is invoked after the DOM modifications have been painted.
Calculations that cost a lot of money are, well, pricey. These can have a significant impact on the effectiveness of your application if mishandled. When working with browser-based applications, you must be careful not to prevent the users from seeing visual changes merely because you're performing a complex calculation in the background. In terms of how complex calculations are handled, useEffect and useLayoutEffect behave differently. As previously stated, useEffect will wait for the execution of the effect mechanism until after the DOM modifications have been painted, making it the clear winner.
The official React documentation suggests using the useEffect as the most preferred option. Ideally, there is a 99% probability that useEffect will suit most use cases, regardless of the application — big or small. As useLayoutEffect is synchronous, React waits to finish the ongoing activity and updates the screen.
Rule thumb: Suppose it's an App component that would wait to update until the useLayoutEffect run is completed. This pauses the React component for seconds because it actively waits for an activity to finish. Consequently, there might be a performance drop, and hence useLayoutEffect is not a good recommendation.
When dealing with inconsistencies in visual changes, useLayoutEffect shines. You get a flicker with useEffect even before DOM changes are drawn, which was caused by how refs are carried on to custom Hooks. These refs are initially set to null before being set when the associated DOM node is rendered.
Using useLayoutEffect versus useEffect makes more sense if you are working with animation. Generally, useLayoutEffect is a yes-yes if you are dealing with ref:
React.useLayoutEffect(() => {
console.log(ref.current)
})Here, the useLayoutEffect waits until the next value get appended. Once the new value gets updated, it entices forward onto the other piece of code. This improves the animation flickering, which usually happens with the useEffect hook.
If you rely on these references to trigger an animation as soon as the element is mounted, you'll notice a distracting flickering of browser paints before your energy starts. It holds for useEffect but not for useLayoutEffect.Opting for the UseLayoutEffect can sometimes provide animations that seem butterier, cleaner, and faster than useEffect.
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Defaults are the key. Before React runs your code, the default value is to let the browser repaint depending on DOM updates. As a result, your code will not stop the browser, and the user will view DOM updates sooner. So, for the most part, useEffect is the way to go. The differences between the useEffect and useLayoutEffect hooks have been examined. However, when working with sophisticated user interface animations, test both Hooks.
Furthermore, you can check similar topics from Knowledgehut blogs. If you are new to React, enroll yourself in the KnowledgeHut’s React JS online training and get a competitive edge over your peers.
Happy Learning!
The useLayoutEffect hook is similar to the useEffect theme in that it fires synchronously once all DOM loading is completed, rather than asynchronous like the useEffect hook. This can be used to re-render the DOM and read its layout concurrently.
The useEffect and useLayoutEffect hooks differ in the order in which they are invoked. After the DOM has been painted, the useEffect theme is called. On the other hand, the useLayoutEffect article is called synchronously before making any changes to the screen.
The signature is similar to useEffect, but it triggers after all DOM updates synchronously. Use this to read structure from the DOM and re-render it synchronously. Before the browser gets a chance to paint, updates queued within useLayoutEffect will be flushed synchronously.
Uselayouteffect as a React Hook makes it easy to inject Javascript into any React component. It helps developers create reusable and consistent components that do not use stateful logic.
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