Delete without refresh

Question

A script that allows you to cast a delete vote on a post immediately after casting a downvote that makes the post score negative, without having to refresh the whole page.

// ==UserScript==
// @name     Stack Exchange: “Delete” without refresh
// @match    https://*.stackexchange.com/*
// @match    https://*.superuser.com/*
// @match    https://*.stackoverflow.com/*
// @match    https://*.mathoverflow.net/*
// @match    https://*.serverfault.com/*
// @match    https://*.askubuntu.com/*
// @exclude  https://chat.stackexchange.com/*
// @exclude  https://api.stackexchange.com/*
// @exclude  https://data.stackexchange.com/*
// @exclude  https://openid.stackexchange.com/*
// @exclude  https://area51.stackexchange.com/*
// @exclude  https://stackexchange.com/*
// @exclude  https://contests.stackoverflow.com/*
// @exclude  /^https?:\/\/winterbash\d{4,}\.stackexchange\.com\//
// ==/UserScript==

document.addEventListener('click', ev => {
  const btn = ev.target.closest('.js-vote-down-btn');
  if (!btn)
    return;
  
  const postContainer = btn.closest('.js-question, .js-answer');
  if (!postContainer)
    return;
  
  const postId = postContainer.dataset.answerid ?? postContainer.dataset.questionid;
  
  const voteWasCast = new Promise((ok, ko) => {
    const handler = cloneInto((ev, jqxhr, opts) => {
      if (!opts.url.startsWith(`/posts/${postId}/vote/`))
        return;
      if (jqxhr.statusText === 'success')
        ok(jqxhr.responseJSON);
      else
        ko(new Error(jqxhr.statusText));
    }, unsafeWindow, { cloneFunctions: true });

    unsafeWindow.eval(`((func) => {
        const cb = (...args) => {
        if (func(...args))
            jQuery(document).off('ajaxComplete', cb);
      };

        jQuery(document).on('ajaxComplete', cb);
    });`)(handler);
  });
  
  (async () => {
    const response = await voteWasCast;
    
    if (!response.Success || response.NewScore > 0)
      return;

    const resp = await fetch(`${location.origin}/posts/ajax-load-realtime/${postId}`);
    const data = await resp.json();
    const frag = document.createRange().createContextualFragment(data.Html);
    
    const newPostMenu = frag.querySelector('.js-post-menu');
    if (!newPostMenu) {
        console.warn(`[SE:Dwr] post menu not found in `, frag);
      return;
    }

    const origPostMenu = postContainer.querySelector('.js-post-menu');
    origPostMenu.parentNode.replaceChild(newPostMenu, origPostMenu);
  })().catch(e => {
    console.warn(`[SE:Dwr] `, e);
  });
});