Add a bell emoji to unread comments on HackerNews

hackernews-new-comms.js

// Can be used with https://github.com/xcv58/Custom-JavaScript-for-Websites-2
// This snippet is released under the terms of the CC0 license: https://creativecommons.org/publicdomain/zero/1.0/deed.en

// Updated by sillysaurusx (v0.1.0):
// - bells stay till you mouseover each HN comment
// - use a constant localStorage key
// future plans:
// - don't bell your own comments
// - a button to un-bell the current page (or comment subtree)

const url = "HN note comments";
const cache = JSON.parse(localStorage.getItem(url) || '{}')

document.querySelectorAll('.athing.comtr').forEach(comm => {
  if (!cache[comm.id]) {
    const span = document.createElement('span');
    span.innerHTML = '🔔' // :bell: emoji
    span.onmousemove = comm.onmousemove = e => {
      console.log('noted ' + comm.id);
      span.remove();
      comm.onmousemove = null;
      cache[comm.id] = Date.now();
      localStorage.setItem(url, JSON.stringify(cache));
    }
    comm.querySelector('.comhead').append(span);
  }
})