share-mastodon.user.js

// ==UserScript==
// @name        Mastodon Share via MenuCommand
// @namespace   net.mizle
// @version     1.0.0
// @description Share current page to Mastodon via GM_registerMenuCommand
// @match       *://*/*
// @grant       GM_registerMenuCommand
// ==/UserScript==

const SERVER = "stellaria.network";

function shareToMastodon() {
  let note = window.getSelection().toString();
  let noteText = "";
  if (note) {
    // 改行ごとに "> " を付与
    noteText = "\n> " + note.split("\n").join("\n> ");
  }
  const text = `${document.title}\n${location.href}${noteText}\n`;
  const url = `https://${SERVER}/share?text=${encodeURIComponent(text)}`;
  window.open(url, "_blank");
}

GM_registerMenuCommand("Share to Mastodon", shareToMastodon);