如何使用内联样式在滚动时使用 transform: rotate() 和 react.js

Question

Creating this page. I have an element I want to rotate on scroll. Would prefer to use react syntax to create this 'animation'.

LeftGear = () =>  {
const rotate = window.scrollY / 10 % Math.PI

const divStyle = {
  backgroundColor: 'purple',
  transform: `scroll(${rotate})`,
}

return  <img
          className={this.changeClassName('circleImage')}
          src="../../assets/icons/red-gear.svg"
          alt="Circles Icon"
          style={divStyle}
        />
}

render(){
  return <LeftGear/>  
}

this works to give the image a background but does not work for that scroll. So Im wondering what I'm doing wrong ?

Answer 1

Rotations work with transform: rotate({n}deg) where {n} is your radius number. For the rest, bind and event listener to the window in an useEffect hook. Instead of updating the divStyle object, just create a reference to the image and update the style.transform property.

React has no smart way of dealing with this, so sometimes you just have to use some vanilla JS.

import React, { useEffect, useRef } from 'react';

const LeftGear = () => {
  const imageRef = useRef();
  const divStyle = {
    backgroundColor: 'purple',
  }

  useEffect(() => {
    window.addEventListener('scroll', event => {
      requestAnimationFrame(() => {
        const rotation = window.scrollY / 10 % Math.PI;
        imageRef.current.style.transform = `rotate(${rotation}deg)`;
      });
    });
  }, []);

  return (
    <img
      ref={imageRef}
      className={this.changeClassName('circleImage')}
      src="../../assets/icons/red-gear.svg"
      alt="Circles Icon"
      style={divStyle}
    />
  )
}