Why expose an API from a React component?

An API allows other parts of your front-end app to interact with the component
in a controlled manner. It can be especially useful when you need to interact
with a component from outside your React root element.
A prime example are web-components, custom HTML elements that can be used and controlled from any webpage.

In this short post, we'll look at leveraging the useImperativeHandle hook to expose functions as an API.

Basic example

The useImperativeHandle hook lets you take control of a component instance from
its parent. It takes two arguments: the ref object passed from the parent
component, and an object that defines the exposed functions.

Here's an example:

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

const ChildWithRef = forwardRef((props, ref) => {
  useImperativeHandle(ref, () => ({
    sayHello: () => {
      console.log('Hello!')
    }
  }))

  return <div>I am a child with a ref</div>
})

const Parent = () => {
  const childRef = useRef(null)

  const handleSayHello = () => {
    childRef.current.sayHello()
  }

  return (
    <div>
      <ChildWithRef ref={childRef} />
      <button onClick={handleSayHello}>Say hello</button>
    </div>
  )
}

In this example, we expose a sayHello function from the ChildWithRef component. This function can be called from the parent using the ref object passed to the child.

Interactive example

Here's a more practical example that exposes an API to control the behavior of a 3D cube.
To allow for more control,You could store the ref in a global variable and use
its API from anywhere in your front-end.