fp-emoji.user.js

// ==UserScript==
// @name         Emoji input replacer
// @version      0.1.1
// @description  replace emojis in input with escaped html entities
// @author       Chad Lavimoniere
// @include      http*://6.*.org/*
// @grant        none
// ==/UserScript==

(function() {
  'use strict';

  /**
   * Implemented so that common unicode chars don't get swept up in the mix, like ç, ñ, é, etc
   * 
   * cf. https://jrgraphix.net/r/Unicode/
   */
  const UNICODE_CUTOFF = 8399;

  // slightly modified from https://dev.to/nikkimk/converting-utf-including-emoji-to-html-x1f92f-4951
  const utf2Html = (s) => {
    return [...s].map((c) => c.codePointAt() > UNICODE_CUTOFF ? `&#${c.codePointAt()};` : c).join("");
  };

  const replacer = (e) => {
    const newValue = utf2Html(e.target.value);
    e.target.value = newValue;
  };

  document.querySelector("#id_body")?.addEventListener("input", replacer);
  document.querySelector("#id_comment-body")?.addEventListener("input", replacer);
})();