github-cdn.js

// ==UserScript==
// @name         Gh Jsdelivr
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  try to take over the world!
// @author       You
// @match        https://github.com/*/*
// @icon         https://www.google.com/s2/favicons?domain=github.com
// @grant        none
// ==/UserScript==

;(function () {
  const main = () => {
    if (location.search !== '?cdn') return
    const user = document.querySelector('.author a').textContent
    const repo = document.querySelector('[itemprop=name] a').textContent
    const branch = document.querySelector(
      '.css-truncate-target[data-menu-button]'
    ).textContent

    const files = Array.from(
      document.querySelectorAll('.js-navigation-open[title]')
    )

    files.forEach(file => {
      const a = document.createElement('a')
      a.href = `https://cdn.jsdelivr.net/gh/${user}/${repo}@${branch}/${encodeURIComponent(
        file.getAttribute('title')
      )}`
      a.target = '_blank'
      a.textContent = 'cdn'
      a.style.marginRight = '8px'
      file.before(a)
    })
  }

  const waitEl = (callback, ...selectors) => {
    let index = 0
    const handle = setInterval(() => {
      if (selectors.every(selector => !!document.querySelector(selector))) {
        clearInterval(handle)
        callback()
      }
      index++
      if (index >= 10) {
        clearInterval(handle)
      }
    }, 1000)
  }

  waitEl(
    main,
    '.author a',
    '[itemprop=name] a',
    '.css-truncate-target[data-menu-button]',
    '.js-navigation-open[title]'
  )
})()