A ViolentMonkey/GreaseMonkey/TamperMonkey script for opening mailto: links in Outlook.com

mailto:outlook.com.js

// ==UserScript==
// @name Outlook mailto: Handler
// @namespace Violentmonkey Scripts
// @match https://outlook.live.com/*
// @grant none
// @version 0.0.2.20190821021306
// @updateUrl https://gist.githubusercontent.com/fallaciousreasoning/3d0928be6f26778548de2d84778c3bb8/raw/mailto:outlook.com.js
// @description Let's Outlook.com open mailto: links
// ==/UserScript==

navigator.registerProtocolHandler("mailto",
                                 "https://outlook.live.com/mail/0/deeplink/compose?mailto=%s",
                                 "Outlook");

const isMailToHandler = () => {
  const params = new URLSearchParams(window.location.search);
  
  const mailto = params.get('mailto');
  if (!mailto)
     return false;
  
  const sansScheme = mailto.split(':')[1];
  const [to, queryString] = sansScheme.split('?');
  const queryParams = new URLSearchParams(queryString);
  queryParams.append('to', to);
  
  // Convert keys to lower case (or Outlook doesn't recognise them).
  for (const [key, value] of queryParams) {
    queryParams.delete(key);
    queryParams.set(key.toLowerCase(), value);
  }
    
  return queryParams.toString();
}

const mailToSearch = isMailToHandler();

if (mailToSearch) {
  window.location.search = mailToSearch;
}