I am following a Udemy course on how to register events with hooks, the instructor gave the below code:
const [userText, setUserText] = useState('');
const handleUserKeyPress = event => {
const { key, keyCode } = event;
if (keyCode === 32 || (keyCode >= 65 && keyCode <= 90)) {
setUserText(`${userText}${key}`);
}
};
useEffect(() => {
window.addEventListener('keydown', handleUserKeyPress);
return () => {
window.removeEventListener('keydown', handleUserKeyPress);
};
});
return (
<div>
<h1>Feel free to type!</h1>
<blockquote>{userText}</blockquote>
</div>
);
Now it works great but I'm not convinced that this is the right way. The reason is, if I understand correctly, on each and every re-render, events will keep registering and deregistering every time and I simply don't think it is the right way to go about it.
So I made a slight modification to the useEffect hooks to below
useEffect(() => {
window.addEventListener('keydown', handleUserKeyPress);
return () => {
window.removeEventListener('keydown', handleUserKeyPress);
};
}, []);
By having an empty array as the second argument, letting the component to only run the effect once, imitating componentDidMount. And when I try out the result, it's weird that on every key I type, instead of appending, it's overwritten instead.
I was expecting setUserText(${userText}${key}); to have new typed key append to current state and set as a new state but instead, it's forgetting the old state and rewriting with the new state.
Was it really the correct way that we should register and deregister event on every re-render?
