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React Hook recipe from https://usehooks.com
import { useState, useCallback, useRef } from "react";
// Usage
function App() {
const [hoverRef, isHovered] = useHover();
return (
<div ref={hoverRef}>
{isHovered ? '😁' : '☹️'}
</div>
);
}
// Hook
function useHover() {
const [value, setValue] = useState(false);
// Wrap in useCallback so we can use in dependencies below
const handleMouseOver = useCallback(() => setValue(true), []);
const handleMouseOut = useCallback(() => setValue(false), []);
// Keep track of the last node passed to callbackRef
// so we can remove its event listeners.
const ref = useRef();
// Use a callback ref instead of useEffect so that event listeners
// get changed in the case that the returned ref gets added to
// a different element later. With useEffect, changes to ref.current
// wouldn't cause a rerender and thus the effect would run again.
const callbackRef = useCallback(
node => {
if (ref.current) {
ref.current.removeEventListener("mouseover", handleMouseOver);
ref.current.removeEventListener("mouseout", handleMouseOut);
}
ref.current = node;
if (ref.current) {
ref.current.addEventListener("mouseover", handleMouseOver);
ref.current.addEventListener("mouseout", handleMouseOut);
}
},
[handleMouseOver, handleMouseOut]
);
return [callbackRef, value];
}
@abirmingham
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abirmingham commented Nov 22, 2019

Just curious... will useCallback(null) be called when the App is unmounted? Otherwise it appears that there is a memory leak here, where removeEventListener would be called on <div> rebinds but not App unmount.

EDIT: It does appear that useCallback(null) is called, which means that my concerns about the memory leak were unfounded.

@therealparmesh
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therealparmesh commented Jan 30, 2020

Should you use useEffect to handle subscribing/unsubscribing logic in a manner that is guaranteed to be safe by React? See https://github.com/therealparmesh/use-hovering.

@mbelsky
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mbelsky commented Feb 14, 2020

Thanks for sharing! I've typed this hook with Typescript, you may find it here: https://gist.github.com/mbelsky/72c1117a63489daf8e6067049d4532d0

@jjenzz
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jjenzz commented Mar 25, 2020

Thoughts on changing the event handlers to mouseenter/mouseleave to prevent the bubbling issue? https://codesandbox.io/s/recursing-goldberg-7mtvc

  • open console
  • hover the button edges and then;
  • hover the kitten

@mbelsky
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mbelsky commented Mar 25, 2020

^ this is best solution that I've found. So +1. Also it could be used in original use-hover

@therealparmesh
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therealparmesh commented Mar 25, 2020

I concur with mouseenter and mouseleave! Great idea.

@abirmingham
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abirmingham commented Mar 25, 2020

+1 - mouseenter/mouseleave is what I'm using in my implementation of this behavior.

@mkamalkayani
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mkamalkayani commented Apr 20, 2020

After using a similar hook to show an element on hover, I realised that I can use onMouseEnter and onMouseLeave to get the same results.

// Usage
function App() {
  const [isHovered, setIsHovered] = React.useState();

  return (
    <div 
     onMouseEnter={()=> setIsHovered(true)}
     onMouseLeave={()=> setIsHovered(false)}
     >
      {isHovered ? '😁' : '☹️'}
    </div>
  );
}

@Andrewnt219
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Andrewnt219 commented May 26, 2020

After using a similar hook to show an element on hover, I realised that I can use onMouseEnter and onMouseLeave to get the same results.

// Usage
function App() {
  const [isHovered, setIsHovered] = React.useState();

  return (
    <div 
     onMouseEnter={()=> setIsHovered(true)}
     onMouseLeave={()=> setIsHovered(false)}
     >
      {isHovered ? '😁' : '☹️'}
    </div>
  );
}

It's all about reusability.

@KymaniHanson
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KymaniHanson commented Nov 11, 2020

Can someone explain line 37 for me?

@ulises-castro
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ulises-castro commented Oct 24, 2021

@KymaniHanson, basically they are assigning the node element to the ref value.
Where node element is your component which is using the hook ref. (line 8)

For more details check the official docs
https://reactjs.org/docs/hooks-faq.html#how-can-i-measure-a-dom-node

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