Capturing the “scroll down” event?

Question

I\'m designing a very simple web page (HTML only), the only \"feature\" I want to implement is to do something when the user scrolls down the page, is there a way to capture

Answer 1

Check if the user scrolled up and simply return

window.addEventListener(
  "scroll",
  e => {
    const scrolled = window.scrollY; // Number of pixels the user has scrolled
    let lastScrolled = 0; // Number of pixels the user has scrolled in the last event

    // If the user scrolls down, the scrolled value goes up and vice versa
    // So basically
    if (scrolled < lastScrolled) {
      // Then the user scrolled up!
      console.log("GET OUT! YOU SCROLLED UP!");
      // But you should update the lastScrolled value nonetheless
      lastScrolled = scrolled;
      return; // And then get out!
    }
    lastScrolled = scrolled; // The value gets updated in any case
    // And your code goes here
  },
  false
);