fade-twitter.js

// ==UserScript==
// @name         Fade Twitter
// @namespace    http://tampermonkey.net/
// @version      0.3
// @description  fades twitter over time and by scrolling to protect me from myself
// @author       You
// @match        https://twitter.com/*
// @grant        none
// ==/UserScript==

const isoDay = () => (new Date()).toISOString().split('T')[0]
const storageKey = `fade-twitter-by-${isoDay()}`
const fadeAmount = () => parseFloat(localStorage[storageKey] || '1.0', 10)

let lastScroll = 0
let debounce = false

let isActive = true

document.addEventListener("visibilitychange", function() {
    isActive = document.visibilityState || document.hasFocus()
});

const fade = (reason = 'on timer') => {
    if (isActive === 'hidden') {
        return
    }

    const f = fadeAmount()
    document.body.style.opacity = f
    localStorage[storageKey] = ''+ (f * 0.99)
    console.log({thisFade: reason, fadeTo: f})
}

const onScroll = (e) => {
  if (!debounce) {
    window.requestAnimationFrame(() => {
      const nextScroll = window.scrollY
      const scrolledBy = lastScroll - nextScroll
      if (Math.abs(scrolledBy) > 1000) {
          lastScroll = nextScroll
          fade('on scrolling')
      }
      debounce = false
    });

    debounce = true
  }
}

document.addEventListener('scroll', onScroll)
window.setInterval(fade, 30000)
fade()