4chan Base64 Decode Tool

appears in the thread page. auto recursive decoding if the message is coded multiple times.

You will need to install an extension such as Tampermonkey, Greasemonkey or Violentmonkey to install this script.

You will need to install an extension such as Tampermonkey to install this script.

You will need to install an extension such as Tampermonkey or Violentmonkey to install this script.

You will need to install an extension such as Tampermonkey or Userscripts to install this script.

You will need to install an extension such as Tampermonkey to install this script.

You will need to install a user script manager extension to install this script.

(I already have a user script manager, let me install it!)

You will need to install an extension such as Stylus to install this style.

You will need to install an extension such as Stylus to install this style.

You will need to install an extension such as Stylus to install this style.

You will need to install a user style manager extension to install this style.

You will need to install a user style manager extension to install this style.

You will need to install a user style manager extension to install this style.

(I already have a user style manager, let me install it!)

// ==UserScript==
// @name         4chan Base64 Decode Tool
// @namespace    https://github.com/x94fujo6rpg/SomeTampermonkeyScripts
// @version      0.01
// @description  appears in the thread page. auto recursive decoding if the message is coded multiple times.
// @author       x94fujo6
// @match        https://boards.4chan.org/*/thread/*
// @match        https://boards.4channel.org/*/thread/*
// ==/UserScript==
/* jshint esversion: 9 */

(function () {
	let
		elem = {
			tool: "decode_tool",
			in: "decode_input",
			out: "decode_output",
			decode: "decode_shit",
			copy: "decode_copy",
			open: "decode_open",
			close: "decode_close",
		},
		box = document.createElement("div"),
		class_list = {
			title: "usTitle",
			box: "usBox",
			t: "usTextBox",
			b: "usButton line-2-item",
		},
		getIn = () => document.getElementById(elem.in).value,
		getOut = () => document.getElementById(elem.out).value,
		setIn = (t = "") => document.getElementById(elem.in).value = t,
		setOut = (t = "") => document.getElementById(elem.out).value = t,
		decode_text = () => {
			let text = getIn(),
				count = 0,
				max = 100,
				[err, output] = decoder(text),
				last_output = output,
				err_msg = "decode failed";
			setIn();
			console.log(count, text);
			if (err) {
				setOut(err_msg);
				console.log(err_msg);
			}
			while (!err && output.length && count < max) {
				count++;
				console.log(count, last_output);
				setOut(last_output);
				[err, output] = decoder(last_output);
				if (err) {
					console.log("end loop");
					break;
				} else {
					setIn(last_output);
					last_output = output;
				}
			}

			function decoder(_t = "") {
				let out = false,
					error = false;
				try {
					out = atob(_t);
				} catch (e) {
					error = e;
				} finally {
					return [error, out];
				}
			}
		},
		copy = () => {
			let text = document.getElementById(elem.out);
			text.select();
			text.setSelectionRange(0, 99999);
			document.execCommand("copy");
		},
		open = () => document.getElementById(elem.tool).style.display = "",
		close = () => document.getElementById(elem.tool).style.display = "none";

	box.className = class_list.box;
	box.innerHTML = `
		<div class="${class_list.title}">Base64 Decode Tool</div>
		<div id="${elem.tool}" style="display: none;">
			<button type="button" id="${elem.decode}" class="${class_list.b}">Decode Input</button>
			<button type="button" id="${elem.copy}" class="${class_list.b}">Copy Output</button>
			<textarea id="${elem.in}" class="${class_list.t}" rows="10" cols="70" placeholder="input"></textarea>
			<textarea id="${elem.out}" class="${class_list.t}" rows="10" cols="70" placeholder="output"></textarea>
		</div>
		<button type="button" id="${elem.open}" class="${class_list.b}">Open</button>
		<button type="button" id="${elem.close}" class="${class_list.b}">Close</button>
	`;
	addCss();
	document.body.appendChild(box);
	document.getElementById(elem.decode).onclick = () => decode_text(false);
	document.getElementById(elem.copy).onclick = () => copy();
	document.getElementById(elem.open).onclick = () => open();
	document.getElementById(elem.close).onclick = () => close();

	function addCss() {
		let s = document.createElement("style");
		document.head.appendChild(s);
		s.textContent = `
			.usTitle {
				display: block;
				font-size: large;
				margin: auto;
				width: 20rem;
				padding: 0.5rem;
			}

			.usBox {
				position: fixed;
				bottom: 1rem;
				right: 1rem;
				z-index: 100;
				border: 2px ridge rgba(0, 0, 0, 0.3);
				background-color: rgba(255, 255, 255, 0.75);
				display: block;
				width: max-content;
				height: max-content;
				text-align: center;
			}

			.usTextBox {
				display: flex;
				width: 95%;
				height: 35%;
				margin: 0.2rem auto;
				word-break: break-all;
			}

			.usButton {
				display: inline;
				margin: 0.25rem;
				padding: 0.5rem;
				text-align: center;
				font-size: large;
			}

			.line-2-item {
				max-width: 100%;
				width: calc(90% / 2);
			}
		`;
	}
})();