Delay React onMouseOver event

问题

I have a list of elements, when hovering one of these, I'd like to change my state.

<ListElement onMouseOver={() => this.setState({data})}>Data</ListElement>

Unfortunately, if I move my mouse over the list, my state changes several times in a quick succession. I'd like to delay the change on state, so that it waits like half a second before being fired. Is there a way to do so?

回答1:

Here's a way you can delay your event by 500ms using a combination of onMouseEnter, onMouseLeave, and setTimeout.

Keep in mind the state update for your data could be managed by a parent component and passed in as a prop.

import React, { useState } from 'react'

const ListElement = () => {
    const [data, setData] = useState(null)
    const [delayHandler, setDelayHandler] = useState(null)

    const handleMouseEnter = event => {
        setDelayHandler(setTimeout(() => {
            const yourData = // whatever your data is

            setData(yourData)
        }, 500))
    }

    const handleMouseLeave = () => {
        clearTimeout(delayHandler)
    }

    return (
        <div
            onMouseEnter={handleMouseEnter}
            onMouseLeave={handleMouseLeave}
        >
            I have a delayed event handler
        </div>
    )
}

export default ListElement

回答2:

You can create a method that will trigger the onMouseOver event when matching special requirements.

In the further example, it triggers after 500 ms.

/**
 * Hold the descriptor to the setTimeout
 */
protected timeoutOnMouseOver = false;

/**
 * Method which is going to trigger the onMouseOver only once in Xms
 */
protected mouseOverTreatment(data) {
   // If they were already a programmed setTimeout
   // stop it, and run a new one
   if (this.timeoutOnMouseOver) {
     clearTimeout(this.timeoutOnMouseOver);
   }

   this.timeoutOnMouseOver = setTimeout(() => {
      this.setState(data);

      this.timeoutOnMouseOver = false;
   }, 500);
}

回答3:

You can use debounce as a dedicated package or get it from lodash, etc:

Useful for implementing behavior that should only happen after a repeated action has completed.

const debounce = require('debounce');

class YourComponent extends Component {
  constructor(props) {
    super(props);

    this.debouncedMouseOver = debounce(handleMouseOver, 200);
  }

  handleMouseOver = data => this.setState({ data });

  render() {
    const data = [];
    return <ListElement onMouseOver={() => this.debouncedMouseOver(data)}>Data</ListElement>;
  }
}

来源：https://stackoverflow.com/questions/50466734/delay-react-onmouseover-event