How do I window removeEventListener using React useEffect

Question

In React Hooks documents it is shown how to removeEventListener during the component's cleanup phase. https://reactjs.org/docs/hooks-reference.html#conditionally-firing-an-effect

In my use case, I am trying to removeEventListener conditional to a state property of the functional component.

Here's an example where the component is never unmounted but the event listener should be removed:

function App () {   const [collapsed, setCollapsed] = React.useState(true);    React.useEffect(     () => {       if (collapsed) {         window.removeEventListener('keyup', handleKeyUp); // Not the same "handleKeyUp" :(       } else {         window.addEventListener('keyup', handleKeyUp);       }     },     [collapsed]   );    function handleKeyUp(event) {     console.log(event.key);     switch (event.key) {       case 'Escape':         setCollapsed(true);         break;     }   }    return collapsed ? (     <a href="javascript:;" onClick={()=>setCollapsed(false)}>Search</a>   ) : (     <span>       <input placeholder="Search" autoFocus />&nbsp;       <a href="javascript:;">This</a>&nbsp;       <a href="javascript:;">That</a>&nbsp;       <input placeholder="Refinement" />     </span>   ); } ReactDOM.render(<App />, document.body.appendChild(document.createElement('div'))); 

(Live sample at https://codepen.io/caqu/pen/xBeBMN)

The problem I see is that the handleKeyUp reference inside removeEventListener is changing every time the component renders. The function handleKeyUp needs a reference to setCollapsed so it must be enclosed by App. Moving handleKeyUp inside useEffect also seems to fire multiple times and lose the reference to the original handleKeyUp.

How can I conditionally window.removeEventListener using React Hooks without unmounting the component?

Answer 1

You can put the handleKeyUp function inside of the function given to useEffect (which is the recommended way of doing it according to the official documentation) and only add the listener and return a cleanup function when collapsed is false.

useEffect(() => {   if (collapsed) {     return;   }    function handleKeyUp(event) {     switch (event.key) {       case "Escape":         setCollapsed(true);         break;     }   }    window.addEventListener("keyup", handleKeyUp);   return () => window.removeEventListener("keyup", handleKeyUp); }, [collapsed]);