What is useImperativeHandle?

The useImperativeHandle hook is a React hook that allows you to customize the value returned from a forwarded ref. This can be useful for a variety of reasons, such as adding new methods to a ref, or changing the behavior of an existing method.

How to use useImperativeHandle

The basic structure of useImperativeHandle is as follows:

useImperativeHandle(ref, customRef, dependencies?)

• ref represents the ref prop passed down from the parent component.

• customRef is a function that returns the customized ref handle, which can be called from the parent ref. This function should return an object that contains the new methods or behavior that you want to add to the ref.

• dependencies is an optional array that determines how often useImperativeHandle is recreated (as with useEffect). If no dependency is added, the useImperativeHandle is re-created each time the component is rendered.

Basic Example

The function that you pass to useImperativeHandle should return an object that contains the new methods or behavior that you want to add to the ref. For example, the following code adds a new method to a ref:

import React, { useImperativeHandle, useRef } from 'react'

function DeleteModal({ open, onClose }, ref) {
  const closeRef = useRef()
  const confirmRef = useRef()

  useImperativeHandle(ref, () => {
    return {
      closeBtn: closeRef.current,
      confirmBtn: confirmRef.current
    }
  })

  if (!open) return null

  return (
    <div>
      <button ref={closeRef} onClick={onClose}>X</button>
      <h1>Delete Item</h1>

      <p>Are you sure you want to delete this item?</p>
      <p>This action cannot be undone</p>

      <button ref={confirmRef}>Confirm</button>
    </div>
  )
}

export default React.forwardRef(DeleteModal)

Now, you can call the focus method on any of the refs from any component that has access to it:

import { useRef, useState } from 'react'
import DeleteModal from './DeleteModal'

function App() {
  const [open, setOpen] = useState(false)
  const modalRef = useRef()

  return (
    <>

    <button onClick={() => setOpen(true)}>Show Modal</button>

    <button onClick={() => modalRef.current.confirmBtn.focus()}>Focus Confirm Btn</button>

      <DeleteModal
        ref={modalRef}
        open={open}
        onClose={() => setOpen(false)}
      />
    </>
  )
}

Advantages of useImperativeHandle

The useImperativeHandle hook has several advantages, including:

• It allows you to add new methods to refs.

• It allows you to change the behavior of existing methods.

• It can be used to implement imperative logic.

Drawbacks of useImperativeHandle

The useImperativeHandle hook also has a few drawbacks, including:

• It can be difficult to use correctly.

• It can make your code less declarative, (more about imperative vs declarative programming here)

• It can introduce performance problems.

When to use useImperativeHandle

The useImperativeHandle hook should be used sparingly. It is best to use it when you need to add new methods to refs or change the behavior of existing methods. You should avoid using it for general-purpose logic.

Conclusion

The useImperativeHandle hook is a powerful tool that can be used to customize refs. However, it is important to use it carefully. If you are not sure how to use it correctly, you should avoid using it. Alternatively, you can learn more about it in the documentation.