Preview to full image rewrites

rewrites.user.js

// ==UserScript==
// @name URL Rewrite
// @namespace Paars
// @match *://*/*
// @run-at document-start
// @grant none
// ==/UserScript==

const rewrites = [
  {
    name: "gfycat",
    test: location => location.host === "thumbs.gfycat.com",
    action: location => location.href = `https://giant.gfycat.com/${location.pathname.substr(1, location.pathname.indexOf("-") - 1)}.mp4`,
  },
  {
    name: "tumblr",
    test: location => location.host.match(/^\d+\.media\.tumblr\.com$/) && location.pathname.match(/_500\.(\w{3})$/),
    action: location => location.href = location.href.replace(/_500\.(\w{3})$/, "_1280.$1")
  }
]

for (let rewrite of rewrites) {
  console.log("Checking rewrite for", rewrite.name)
  
  if (rewrite.test(window.location)) {
    console.log("succeeded!")
    return rewrite.action(window.location)
  } else {
    console.log("failed...")
  }
}