bangs/startpage.user.js

// ==UserScript==
// @name     Startpage Bangs
// @version  1
// @grant    none
// @run-at   document-start
// @include  https://*.startpage.com/*
// ==/UserScript==

fetch('https://s3.sbruder.de/cdn/bangs/bangs.json')
  .then(text => text.json())
  .then(bangs => {
  const urlParams = new URLSearchParams(window.location.search)
  const searchQuery = urlParams.get('query')

  let matchBang = null
  let parsedBang = null

  matchBang = searchQuery.match(/(.*) \!(.*)/)
  if (matchBang !== null) {
    parsedBang = {
      'bang': matchBang[2].toLowerCase(),
      'query': matchBang[1]
    }
  }

  matchBang = searchQuery.match(/\!(.*) (.*)/)
  if (matchBang !== null) {
    parsedBang = {
      'bang': matchBang[1].toLowerCase(),
      'query': matchBang[2]
    }
  }

  if (parsedBang !== null) {
    redirectURL = bangs[parsedBang.bang].replace('%s', encodeURI(parsedBang.query)).replace('%S', parsedBang.query)
    window.location.replace(redirectURL);
  }
})