Toggle Class based on scroll React JS

Question

I\'m using bootstrap 4 nav bar and would like to change the background color after ig 400px down scroll down. I was looking at the react docs and found a onScroll but couldn\'t

Answer 1

This is yet another take / my take on hooks approach for on scroll displaying and hiding of a random page element.

I have been very much inspired from: Dan Abramov's post here.

You can check a full working example, in this CodeSandbox demo.

The following is the code for the useScroll custom hook:

import React, { useState, useEffect } from "react";

export const useScroll = callback => {
  const [scrollDirection, setScrollDirection] = useState(true);

  const handleScroll = () => {
    const direction = (() => {
      // if scroll is at top or at bottom return null,
      // so that it would be possible to catch and enforce a special behaviour in such a case.
      if (
        window.pageYOffset === 0 ||
        window.innerHeight + Math.ceil(window.pageYOffset) >=
          document.body.offsetHeight
      )
        return null;
      // otherwise return the direction of the scroll
      return scrollDirection < window.pageYOffset ? "down" : "up";
    })();

    callback(direction);
    setScrollDirection(window.pageYOffset);
  };

  // adding and cleanning up de event listener
  useEffect(() => {
    window.addEventListener("scroll", handleScroll);
    return () => window.removeEventListener("scroll", handleScroll);
  });
};

And this hook will be consumed like this:

  useScroll(direction => {
    setScrollDirection(direction);
  });

A full component using this custom hook:

import React, { useState } from "react";
import ReactDOM from "react-dom";
import CustomElement, { useScroll } from "./element";
import Scrollable from "./scrollable";

function Page() {
  const [scrollDirection, setScrollDirection] = useState(null);

  useScroll(direction => {
    setScrollDirection(direction);
  });

  return (
    

      {/* a custom element that implements some scroll direction behaviour */}
      {/* "./element" exports useScroll hook and  */}
      
      {/* just a lorem ipsum long text */}
      
    
  );
}

const rootElement = document.getElementById("root");

ReactDOM.render(, rootElement);

And lastly the code for CustomElement:

import React, { useState, useEffect } from "react";

export default props => {
  const [elementVisible, setElementVisible] = useState(true);
  const { scrollDirection } = props;

  // when scroll direction changes element visibility adapts, but can do anything we want it to do
  // U can use ScrollDirection and implement some page shake effect while scrolling
  useEffect(() => {
    setElementVisible(
      scrollDirection === "down"
        ? false
        : scrollDirection === "up"
        ? true
        : true
    );
  }, [scrollDirection]);

  return (
    

      element
    
  );
};