ReactJS useLayoutEffect Hook

ReactJS is a popular JavaScript library used primarily for building user interfaces. It provides an effective way to simplify the development of complex web applications. In order to enhance the performance of ReactJS, the library offers several Hooks, one of which is useLayoutEffect.

What is useLayoutEffect

useLayoutEffect is a Hook similar to useEffect, but it is synchronous and runs immediately after the component has rendered. This means that useLayoutEffect is more suitable for manipulating the DOM and performing side-effects that depend on the layout of the page, such as calculating the size or position of an element.

How to use useLayoutEffect

useLayoutEffect can be imported from the React library like so:

import { useLayoutEffect } from 'react';

Like other Hooks, useLayoutEffect is used inside a functional component. It takes two arguments, a function that specifies the effect to be performed and an array of dependencies to watch for changes. The effect function is called every time the component re-renders.

useLayoutEffect(() => {
  // effect code goes here
}, [/* array of dependencies */]);

Example use cases

Here are some examples of how useLayoutEffect can be used in practical applications:

Measure the size of an element

import { useLayoutEffect, useState, useRef } from "react";

function Component() {
  const [width, setWidth] = useState(0);
  const elementRef = useRef(null);

  useLayoutEffect(() => {
    setWidth(elementRef.current.offsetWidth);
  }, [elementRef.current]);

  return <div ref={elementRef}>Width is {width}px</div>;
}

In this example, useLayoutEffect takes in a function that sets the width of an element using its offsetWidth property. The effect runs every time the component is rendered, and the updated width is displayed.

Animate a component

import { useLayoutEffect, useRef } from "react";

function Component() {
  const ref = useRef(null);

  useLayoutEffect(() => {
    const element = ref.current;
    element.style.opacity = "0";
    element.animate([{ opacity: "0" }, { opacity: "1" }], {
      duration: 1000,
    });
  }, []);

  return <div ref={ref}>Animate me!</div>;
}

In this example, useLayoutEffect is used to animate a component using the web animations API. The effect runs once when the component is mounted, animating the opacity of the element from 0 to 1 over a duration of 1 second.

Conclusion

In conclusion, useLayoutEffect is a useful Hook for manipulating the DOM and performing side-effects that depend on the layout of the page. However, it should be used with caution, as it can negatively impact the performance of your application if used improperly.