Plurk jQuery patch

Plurk_jQuery_patch.js

// ==UserScript==
// @name         Plurk jQuery patch
// @namespace    http://www.plurk.com/
// @include      http://www.plurk.com/*
// @include      https://www.plurk.com/*
// @version      0.1
// @description  Reconnect jQuery for Plurk.com
// @author       Mist Poryvaev
// @grant none
// @run-at       document-start
// ==/UserScript==
// based on https://github.com/jspenguin2017/Snippets/blob/master/onbeforescriptexecute.html
        // Library code, licensed under MIT
        (() => {
            "use strict";

            const Event = class {
                constructor(script, target) {
                    this.script = script;
                    this.target = target;

                    this._cancel = false;
                    this._replace = null;
                    this._stop = false;
                }

                preventDefault() {
                    this._cancel = true;
                }
                stopPropagation() {
                    this._stop = true;
                }
                replacePayload(payload) {
                    this._replace = payload;
                }
            };

            let callbacks = [];
            window.addBeforeScriptExecuteListener = (f) => {
                if (typeof f !== "function") {
                    throw new Error("Event handler must be a function.");
                }
                callbacks.push(f);
            };
            window.removeBeforeScriptExecuteListener = (f) => {
                let i = callbacks.length;
                while (i--) {
                    if (callbacks[i] === f) {
                        callbacks.splice(i, 1);
                    }
                }
            };

            const dispatch = (script, target) => {
                if (script.tagName !== "SCRIPT") {
                    return;
                }

                const e = new Event(script, target);

                if (typeof window.onbeforescriptexecute === "function") {
                    try {
                        window.onbeforescriptexecute(e);
                    } catch (err) {
                        console.error(err);
                    }
                }

                for (const func of callbacks) {
                    if (e._stop) {
                        break;
                    }
                    try {
                        func(e);
                    } catch (err) {
                        console.error(err);
                    }
                }

                if (e._cancel) {
                    script.textContent = "";
                    script.remove();
                } else if (typeof e._replace === "string") {
                    script.textContent = e._replace;
                }
            };
            const observer = new MutationObserver((mutations) => {
                for (const m of mutations) {
                    for (const n of m.addedNodes) {
                        dispatch(n, m.target);
                    }
                }
            });
            observer.observe(document, {
                childList: true,
                subtree: true,
            });
        })();

        // mixed with https://stackoverflow.com/questions/36605989/how-to-replace-head-script-using-greasemonkey-code
        // and https://stackoverflow.com/questions/18120809/equivalent-of-onbeforescriptexecute-in-chrome
        (() => {
            "use strict";
            window.onbeforescriptexecute = (e) => {
                if (e.script.outerHTML.includes("https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js")) {
                    var dst_script = document.createElement('script');
                    dst_script.src = "https://code.jquery.com/jquery-3.3.1.min.js";
                    e.target.replaceChild(dst_script, e.script);
                    e.preventDefault();
                }
            };
        })();