convert-redit-image-urls.user.js

// ==UserScript==
// @name        Convert Reddit hosted image preview URLs to direct image URLs
// @namespace   https://greasyfork.org/en/users/85671-jcunews
// @version     1.0.1
// @license     AGPL v3
// @author      jcunews
// @description Context: https://www.reddit.com/r/GreaseMonkey/comments/yuzgc2/request_script_to_replace_parts_of_a_url/
// @match       *://*/*
// @grant       none
// @run-at      document-start
// ==/UserScript==

//Applies to: URL of images, URL of links, text content of links if same as links' URL, and image URL in browser address bar (i.e. auto redirect).

((rx, m) => {
  function chkEle(link, prop, m) {
    if (m = link[prop].match(rx)) {
      m = m[1] + "i" + m[2];
      if (link.textContent.trim() === link[prop]) link.textContent = m;
      link[prop] = m
    }
  }
  function doNode(node, recurs) {
    switch (node.tagName) {
      case "A":
        chkEle(node, "href");
        break;
      case "IMG":
        chkEle(node, "src");
        break;
      default:
        if (recurs && node.tagName) chkNodes(node.querySelectorAll("a,img"))
    }
  }
  function chkNodes(nodes) {
    nodes.forEach(node => doNode(node, true))
  }
  rx = /^(https:\/\/)preview(\.redd\.it\/[^\.]+\.[a-z]+)\?/;
  if (m = location.href.match(rx)) {
    return location.href = m[1] + "i" + m[2]
  }
  (new MutationObserver(recs => {
    recs.forEach(rec => {
      if (rec.addedNodes) {
        chkNodes(rec.addedNodes)
      } else doNode(rec.target)
    })
  })).observe(document, {childList: true, subtree: true, attributeFilter: ["href", "src"]})
})()