useImperativeHandle hook in react

The useImperativeHandle hook allows you to customize the instance value that is exposed to parent components when using ref. This can be useful when you need to provide a certain interface to parent components, but you don't want to expose all of the internal implementation details of a child component.

Here’s an example of how to use useImperativeHandle:

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

const Input = React.forwardRef((props, ref) => {
  const inputRef = useRef();

  useImperativeHandle(ref, () => ({
    focus: () => {
      inputRef.current.focus();
    },
    value: inputRef.current.value
  }));

  return (
    <input
      type="text"
      ref={inputRef}
      placeholder={props.placeholder}
    />
  );
});

function App() {
  const inputRef = useRef();

  const handleClick = () => {
    inputRef.current.focus();
  };

  return (
    <div>
      <Input ref={inputRef} placeholder="Type here" />
      <button onClick={handleClick}>Focus input</button>
    </div>
  );
}

In this example, we define a custom Input component that uses useImperativeHandle to expose a focus method and a value property to parent components when using ref. The useImperativeHandle hook takes two arguments: the ref object and a callback function that returns an object with the properties and methods that should be exposed to parent components.

In the App component, we use the Input component and pass a ref object to it. We also define a handleClick function that calls the focus method of the inputRef object when a button is clicked.

When you run this code, you’ll see an input field with a placeholder text and a button that says “Focus input”. When you click the button, the focus method of the inputRef object is called, and the input field is focused.

In summary, the useImperativeHandle hook allows you to customize the instance value that is exposed to parent components when using ref. This can be useful when you need to provide a certain interface to parent components but don't want to expose all of the internal implementation details of a child component.