Bro, don't pollute my clipboard!

JustCopyIt.js

// ==UserScript==
// @name         c
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  try to take over the world!
// @author       You
// @match        https://www.zhihu.com/question/*
// @match        https://www.douban.com/note/*
// @grant        none
// @run-at document-end
// ==/UserScript==

(function() {
    'use strict';
    setTimeout(() => {
        document.addEventListener("copy", function (event) {
            event.stopPropagation();
        }, true);
    }, 2000)
})();