tampermonkey scripts learning

codechef-io-copy.user.js

// ==UserScript==
// @name         Codechef IO Copy
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  try to take over the world!
// @author       jiakai
// @match        https://www.codechef.com/problems/*
// @icon         https://www.google.com/s2/favicons?sz=64&domain=tampermonkey.net
// @grant        none
// ==/UserScript==

let styleSheet = `
.copyBtn {
    background-color: green;
    padding: 5px;
    font-size: 12px;
}
`;

let s = document.createElement("style");
s.type = "text/css";
s.innerHTML = styleSheet;
(document.head || document.documentElement).appendChild(s);

window.addEventListener("load", function () {
	"use strict";

	function copy(ele) {
		let temp = document.createElement("textarea");
		document.body.appendChild(temp);
		temp.value = ele.textContent;
		temp.select();
		document.execCommand("copy");
		temp.remove();
	}

	function addCopyBtn(ele) {
		let btn = document.createElement("button");
		btn.innerHTML = "Copy";
		btn.className = "copyBtn";
		btn.onclick = () => {
			copy(ele.lastChild);
		};

		ele.insertBefore(document.createElement("br"), ele.childNodes[0]);
		ele.insertBefore(btn, ele.childNodes[0]);
	}

	let preTags = document.getElementsByTagName("pre");
	console.log(preTags);
	for (let preTag of preTags) {
		addCopyBtn(preTag);
	}
});