In React, the useLayoutEffect hook is similar to the useEffect hook, but it runs synchronously after all DOM mutations. This makes it ideal for manipulating the DOM or performing measurements before the browser paints the screen.

While React provides the useLayoutEffect hook out of the box, we may encounter situations where we need to create our own custom hooks for specific needs. In this blog post, we will walk through the steps to create a custom useLayoutEffect hook.

Why Create a Custom useLayoutEffect Hook?

Creating a custom useLayoutEffect hook allows us to encapsulate logic that needs to be executed synchronously after DOM updates. This can make our code more reusable, modular, and easier to test.

Implementing the Custom useLayoutEffect Hook

To create a custom useLayoutEffect hook, we’ll follow these steps:

1. Import the necessary dependencies:

import { useEffect, useRef } from 'react';

1. Define our custom hook:

const useCustomLayoutEffect = (effect, deps) => {
  const mountedRef = useRef(false);

  useEffect(() => {
    if (mountedRef.current) {
      return effect();
    } else {
      mountedRef.current = true;
    }
  }, deps);
};

In the code above, we create a custom hook called useCustomLayoutEffect. It takes two arguments: effect (the effect function we want to run) and deps (the dependency array). We also create a mountedRef using the useRef hook to keep track of the mount state.

1. Usage:

Now that we have our custom useCustomLayoutEffect hook, we can use it in our components. Here’s an example:

import React from 'react';

const MyComponent = () => {
  useCustomLayoutEffect(() => {
    // DOM manipulation or measurements
    // runs synchronously after DOM update
  }, []);

  // rest of the component logic

  return (
    // component JSX
  );
}

In the example above, we use useCustomLayoutEffect in our functional component MyComponent to perform any DOM manipulations or measurements that need to happen synchronously after the DOM updates.

Conclusion

By creating a custom useLayoutEffect hook, we can encapsulate logic that needs to be executed synchronously after DOM updates. This can make our code more reusable, modular, and easier to test. Remember to be mindful of the performance implications of using useLayoutEffect, as it runs synchronously and may impact rendering performance.

Using custom hooks is a powerful feature in React, allowing us to create reusable abstractions.