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Jsdelivr Auto Fallback

修复 cdn.jsdelivr.net 无法访问的问题

目前为 2022-05-30 提交的版本，查看 最新版本。

  1. // ==UserScript==
  2. // @name Jsdelivr Auto Fallback
  3. // @namespace https://github.com/PipecraftNet/jsdelivr-auto-fallback
  4. // @version 0.2.0
  5. // @author PipecraftNet&DreamOfIce
  6. // @description 修复 cdn.jsdelivr.net 无法访问的问题
  7. // @homepage https://github.com//jsdelivr-auto-fallback
  8. // @supportURL https://github.com/PipecraftNet/jsdelivr-auto-fallback/issues
  9. // @license MIT
  10. // @match *
  11. // @run-at document-start
  12. // ==/UserScript==
  13.  
  14. ((document) => {
  15.   'use strict';
  16.   let fastNode;
  17.   let failed;
  18.   let isRunning;
  19.   const DEST_LIST = [
  20.     'cdn.jsdelivr.net',
  21.     'fastly.jsdelivr.net',
  22.     'gcore.jsdelivr.net',
  23.     'testingcf.jsdelivr.net',
  24.     'test1.jsdelivr.net'
  25.   ];
  26.   const PREFIX = '//';
  27.   const SOURCE = DEST_LIST[0];
  28.   const starTime = Date.now();
  29.   const TIMEOUT = 2000;
  30.   const STORE_KEY = 'jsdelivr-auto-fallback';
  31.   const TEST_PATH = '/gh/PipecraftNet/jsdelivr-auto-fallback@main/empty.css?';
  32.   const shouldReplace = (text) => text && text.includes(PREFIX + SOURCE);
  33.   const replace = (text) => text.replace(PREFIX + SOURCE, PREFIX + fastNode);
  34.   const setTimeout = window.setTimeout;
  35.   const $ = document.querySelectorAll.bind(document);
  36.  
  37.   const replaceElementSrc = () => {
  38.     let element;
  39.     let value;
  40.     for (element of $('link[rel="stylesheet"]')) {
  41.       value = element.href;
  42.       if (shouldReplace(value) && !value.includes(TEST_PATH)) {
  43.         element.href = replace(value);
  44.       }
  45.     }
  46.  
  47.     for (element of $('script')) {
  48.       value = element.src;
  49.       if (shouldReplace(value)) {
  50.         const newNode = document.createElement('script');
  51.         newNode.src = replace(value);
  52.         element.defer = true;
  53.         element.src = '';
  54.         element.before(newNode);
  55.         element.remove();
  56.       }
  57.     }
  58.  
  59.     for (element of $('img')) {
  60.       value = element.src;
  61.       if (shouldReplace(value)) {
  62.         // Used to cancel loading. Without this line it will remain pending status.
  63.         element.src = '';
  64.         element.src = replace(value);
  65.       }
  66.     }
  67.  
  68.     // All elements that have a style attribute
  69.     for (element of $('*[style]')) {
  70.       value = element.getAttribute('style');
  71.       if (shouldReplace(value)) {
  72.         element.setAttribute('style', replace(value));
  73.       }
  74.     }
  75.  
  76.     for (element of $('style')) {
  77.       value = element.innerHTML;
  78.       if (shouldReplace(value)) {
  79.         element.innerHTML = replace(value);
  80.       }
  81.     }
  82.   };
  83.  
  84.   const tryReplace = () => {
  85.     if (!isRunning && failed && fastNode) {
  86.       console.warn(SOURCE + ' is not available. Use ' + fastNode);
  87.       isRunning = true;
  88.       setTimeout(replaceElementSrc, 0);
  89.       // Some need to wait for a while
  90.       setTimeout(replaceElementSrc, 20);
  91.       // Replace dynamically added elements
  92.       setInterval(replaceElementSrc, 500);
  93.     }
  94.   };
  95.  
  96.   const checkAvailable = (url, callback) => {
  97.     let timeoutId;
  98.     const newNode = document.createElement('link');
  99.     const handleResult = (isSuccess) => {
  100.       if (!timeoutId) {
  101.         return;
  102.       }
  103.  
  104.       clearTimeout(timeoutId);
  105.       timeoutId = 0;
  106.       // Used to cancel loading. Without this line it will remain pending status.
  107.       if (!isSuccess) newNode.href = 'data:text/plain;base64,';
  108.       newNode.remove();
  109.       callback(isSuccess);
  110.     };
  111.  
  112.     timeoutId = setTimeout(handleResult, TIMEOUT);
  113.  
  114.     newNode.addEventListener('error', () => handleResult(false));
  115.     newNode.addEventListener('load', () => handleResult(true));
  116.     newNode.rel = 'stylesheet';
  117.     newNode.text = 'text/css';
  118.     newNode.href = url + TEST_PATH + starTime;
  119.     document.head.insertAdjacentElement('afterbegin', newNode);
  120.   };
  121.  
  122.   const cached = (() => {
  123.     try {
  124.       return Object.assign(
  125.         {},
  126.         JSON.parse(GM_getValue(STORE_KEY) || '{}')
  127.       );
  128.     } catch {
  129.       return {};
  130.     }
  131.   })();
  132.  
  133.   const main = () => {
  134.     cached.time = starTime;
  135.     cached.failed = false;
  136.     cached.fastNode = null;
  137.  
  138.     for (const url of DEST_LIST) {
  139.       checkAvailable('https://' + url, (isAvailable) => {
  140.         // console.log(url, Date.now() - starTime, Boolean(isAvailable));
  141.         if (!isAvailable && url === SOURCE) {
  142.           failed = true;
  143.           cached.failed = true;
  144.         }
  145.  
  146.         if (isAvailable && !fastNode) {
  147.           fastNode = url;
  148.         }
  149.  
  150.         if (isAvailable && !cached.fastNode) {
  151.           cached.fastNode = url;
  152.         }
  153.  
  154.         tryReplace();
  155.       });
  156.     }
  157.  
  158.     setTimeout(() => {
  159.       // If all domains are timeout
  160.       if (failed && !fastNode) {
  161.         fastNode = DEST_LIST[1];
  162.         tryReplace();
  163.       }
  164.  
  165.       GM_setValue(STORE_KEY, JSON.stringify(cached));
  166.     }, TIMEOUT + 100);
  167.   };
  168.  
  169.   if (
  170.     cached.time &&
  171.     starTime - cached.time < 60 * 60 * 1000 &&
  172.     cached.failed &&
  173.     cached.fastNode
  174.   ) {
  175.     failed = true;
  176.     fastNode = cached.fastNode;
  177.     tryReplace();
  178.     setTimeout(main, 1000);
  179.   } else {
  180.     main();
  181.   }
  182. })(document);