React hook dependent functions as props - reactjs

Question

After reading through the intro to hooks I have an immediate feeling that it has a performance problem with passing function props.
Consider the following class component, where the function reference is a bound function, so no re-renders happen because of it.
import React from 'react';
class Example extends React.Component {
state = { count: 0 }
onIncrementClicked = () => setState({ count: this.state.count + 1 })
render() {
return (
<div>
<p>You clicked {this.state.count} times</p>
<button onClick={this.onIncrementClicked}>
Click me
</button>
</div>
);
}
}
Now compare it to the hooks-version where we pass a new function on each render to the button. If an <Example /> component renders, there's no way of avoiding the re-rendering of it's <button /> child.
import React, { useState } from 'react';
function Example() {
// Declare a new state variable, which we'll call "count"
const [count, setCount] = useState(0);
return (
<div>
<p>You clicked {count} times</p>
<button onClick={() => setCount(count + 1)}>
Click me
</button>
</div>
);
}
I know it's a small example, but consider a bigger app where many callbacks are passed around that depend on hooks. How could this be optimised?
How would I avoid re-rendering everything that takes a function prop, that depends on a hook?

Answer 1

You can use useCallback to ensure that event handler doesn't change between renders with the same count value:
const handleClick = useCallback(
() => {
setCount(count + 1)
},
[count],
);
For better optimisation you can store count value as an attribute of the button so you don't need access to this variable inside event handler:
function Example() {
// Declare a new state variable, which we'll call "count"
const [count, setCount] = useState(0);
const handleClick = useCallback(
(e) => setCount(parseInt(e.target.getAttribute('data-count')) + 1),
[]
);
return (
<div>
<p>You clicked {count} times</p>
<button onClick={handleClick} data-count={count}>
Click me
</button>
</div>
);
}
Also check https://reactjs.org/docs/hooks-faq.html#are-hooks-slow-because-of-creating-functions-in-render