API for CustomElements in YouTube

A JavaScript tool to modify CustomElements in YouTube
目前为 2023-05-09 提交的版本。查看最新版本。
此脚本不应直接安装，它是一个供其他脚本使用的外部库。如果您需要使用该库，请在脚本元属性加入：// @require https://update.gf.qytechs.cn/scripts/465819/1187694/API%20for%20CustomElements%20in%20YouTube.js
提问、发表评价，或者举报这个脚本。
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// ==UserScript==
// @name         API for CustomElements in YouTube
// @namespace    http://tampermonkey.net/
// @version      1.0
// @description  A JavaScript tool to modify CustomElements in YouTube
// @author       CY Fung
// @grant        none
// @license      MIT
// ==/UserScript==

/*

MIT License

Copyright (c) 2023 cyfung1031

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

*/

const customYtElements = (function () {
  'use strict';

  const postRegistered = (ytElmTag, f) => {
    const ceElmConstrcutor = customElements.get(ytElmTag);
    const proto = ((ceElmConstrcutor || 0).prototype || 0);
    if (proto && ('__hasRegisterFinished' in proto)) {
      f(proto);
    } else if (proto && ('_registered' in proto)) {
      postRegistered_(proto).push(f);
    } else {
      console.warn('[tyt] postRegistered is not supported.');
    }
  }

  const injectorCreationForRegistered = ((mMapOfFuncs, _registered) => {
    if (!(mMapOfFuncs instanceof WeakMap) || (typeof _registered !== 'function')) return console.error('[ytI] Incorrect parameters');
    const $callee = function (...args) {
      const map = mMapOfFuncs;
      const f = _registered;
      if (!f) return console.error('[ytI] the injector is already destroyed.');
      // CE prototype have not yet been "Object.defineProperties()"
      let res = f.call(this, ...args); // normally shall be undefined with no arguments
      // CE prototype have been "Object.defineProperties()"
      let funcs = null;
      try {
        const constructor = this.constructor || null;
        if (!constructor || !constructor.prototype) throw '[ytI] CE constructor is not found or invalid.';
        // constructor.prototype._registered = f; // restore to original
        delete constructor.prototype._registered;
        if (constructor.prototype._registered !== f) {
          constructor.prototype._registered = f;
        }
        funcs = map.get(constructor) || 0;
        if (typeof funcs.length !== 'number') throw '[ytI] This injection function call is invalid.';
        console.debug(`[ytI] ${constructor.prototype.is}'s _registered have been called.`);
        map.set(constructor, null); // invalidate
        for (const func of funcs) {
          func(constructor.prototype); // developers might implement Promise, setTimeout, or requestAnimation inside the `func`.
        }
      } catch (e) {
        console.warn(e);
      } finally {
        if (funcs) funcs.length = 0;
      }
      return res;
    }
    $callee.getMap = () => mMapOfFuncs; // for external
    $callee.getOriginalFunction = () => _registered; // for external
    $callee.destroyObject = function () {
      // in addition to GC
      mMapOfFuncs = null; // WeakMap does not require clear()
      _registered = null;
      this.__injector__ = null;
      this.getMap = null;
      this.getOriginalFunction = null;
      this.destroyObject = null;
    }
    // after all injected _registered are called,
    // customElements.get('ytd-watch-flexy').prototype._registered.__injector__.deref() will become undefined.
    const wrapped = typeof WeakRef === 'function' ? new WeakRef($callee) : $callee;
    $callee.__injector__ = wrapped; // for _registered.__injector__
    return $callee;
  });

  const customYtElements = {
    whenRegistered(ytElmTag, immediateCallback) {
      return new Promise(resolve => {
        if (typeof customElements !== 'object' || typeof customElements.whenDefined !== 'function' || typeof customElements.get !== 'function') console.error('[ytI] customElements (native or polyfill) is not available.');
        const ceReady = () => { // ignore async result; the result in whenDefined is not the same as customElements.get
          postRegistered(ytElmTag, (proto) => {
            if (immediateCallback) immediateCallback(proto);
            resolve(proto);
          });
        }
        customElements.get(ytElmTag) ? ceReady() : customElements.whenDefined(ytElmTag).then(ceReady);
      });
    }
  }

  const postRegistered_ = (ceProto) => { // delay prototype injection
    if (!('_registered' in ceProto)) return console.warn('[ytI] no _registered is found in proto');
    const _registered = ceProto._registered; // make a copy in this nested closure.
    if (typeof _registered !== 'function') return console.warn('[ytI] proto._registered is not a function');
    let injector = null;
    if (injector = _registered.__injector__) {
      if (injector.deref) injector = injector.deref(); // null if _registered of all CEs are restored.
    }
    if (!injector) {
      injector = injectorCreationForRegistered(new WeakMap(), _registered);
      _registered.__injector__ = injector.__injector__;
    }
    if (typeof (injector || 0).getMap !== 'function') return console.warn('[ytI] the injector function is invalid.');
    const mapOfFuncs = injector.getMap();
    const ceConstructor = ceProto.constructor || null;
    if (!ceConstructor) return console.warn('[ytI] no constructor is found in proto');
    let funcs;
    if (!mapOfFuncs.has(ceConstructor)) {
      mapOfFuncs.set(ceConstructor, funcs = []);
      ceProto._registered = injector;
    } else {
      funcs = mapOfFuncs.get(ceConstructor);
    }
    if (!funcs) return console.warn('[ytI] _registered has already called. You can just override the properties.');
    return funcs;
  }
 
  // Export to external environment
  try { window.customYtElements = customYtElements; } catch (error) { /* for Greasemonkey */ }
  try { module.customYtElements = customYtElements; } catch (error) { /* for CommonJS */ }
 
  return customYtElements;

})();
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