JSFiddle - React, Tailwind, and code Playground

HTML

<body>
		<table class="table_main">
	
			<thead>
			<tr>
				<td class="cell_header" colspan="2">Szyfrator v1.1</td>
			</tr>
			</thead>
	
			<tbody>

			<!-- POCZĄTEK MODUŁU SZYFRUJĄCEGO -->
			<tr class="module_encryption">
				<td colspan="2" class="module_header">
					MODUŁ SZYFRUJĄCY
				</td>
			</tr>

			<tr class="module_encryption">
				<td class="cell_buttons">
					<input type="button" class="button" id="encode_button_reveal" value="Ujawnij wynik">
					<input type="button" class="button" id="encode_button_hide" value="Ponownie ukryj wynik">
					<hr style="visibility:hidden;">
					<input type="button" class="button button_copy" id="encode_button_copy" disabled value="Skopiuj wynik do schowka">
					<hr>
					<input type="button" class="button" id="encode_button_clear" value="Wyczyść">
				</td>
				<td class="cell_textareas">
					<textarea class="area" id="encode_input" autofocus></textarea>
					<textarea class="area" id="encode_output" readonly></textarea>
				</td>
				
			</tr>

			<tr class="module_encryption">
				<td class="cell_status" colspan="2"></td>
			</tr>
			<!-- KONIEC MODUŁU SZYFRUJĄCEGO -->

			<tr><td class="cell_spacer" colspan="2"></td></tr>
	
			<!-- POCZĄTEK MODUŁU DESZYFRUJĄCEGO -->
			<tr class="module_decryption">
				<td colspan="2" class="module_header">
					MODUŁ DESZYFRUJĄCY
				</td>
			</tr>
			<tr class="module_decryption">
				<td class="cell_buttons">
					<input type="button" class="button button_copy" id="decode_button_copy" disabled value="Skopiuj wynik do schowka">
					<hr>
					<input type="button" class="button" id="decode_button_clear" value="Wyczyść">
				</td>
				<td class="cell_textareas">
					<textarea class="area" id="decode_input" autofocus></textarea>
					<textarea class="area" id="decode_output" readonly></textarea>
				</td>

			</tr>
			<tr class="module_decryption">
				<td class="cell_status" colspan="2"></td>
			</tr>
			<!-- KONIEC MODUŁU SZYFRUJĄCEGO -->

			</tbody>

		</table>
	</body>

CSS

.table_main {
	width: 640px;
	border: none;
	margin: 0 auto;
	border-collapse: collapse;
}
.module_encryption td {
	margin: 0;
	background-color: lightgreen;
}
.module_decryption td {
	margin: 0;
	background-color: lightblue;
}
.module_header {
	text-align: center;
}
.cell_header {
	text-align: center;
	font-weight: bold;
	padding-bottom: 20px;
}
.cell_buttons {
	width: 200px;
	text-align: center;
}
.cell_textareas {
	text-align: center;
}
.cell_status {
	height: 20px;
}
.cell_spacer {
	height: 10px;
}
.button {
	width: 190px;
	border: 1px solid black;
}
.button_copy {
	background-color: #FF5510;
}
.button_paste {
	background-color: #00FF10;
}
.area {
	width: 200px;
	height: 200px;
	resize: none;
}
#encode_input {
	border: none !important;
	background:
    ...

JavaScript

var event_input = new Event("input", {
    view: window,
    bubbles: true,
    cancelable: true
});

{
	document.addEventListener(
		"DOMContentLoaded",
		function() {
			document.getElementById("encode_input").value = "";
			document.getElementById("encode_output").value = "";
			document.getElementById("decode_input").value = "";
			document.getElementById("decode_output").value = "";
			document.getElementById("encode_input").dispatchEvent(event_input);
			document.getElementById("decode_input").dispatchEvent(event_input);
		}
	);
}

//Encryption logic for textareas
{
	let encode_input	= document.getElementById("encode_input");
	let encode_output	= document.getElementById("encode_output");

	let encode_input_handler = function(e) {
		encode_output.value = encode(e.target.value);
		if(encode_output.value.length) {
			document.getElementById("encode_button_copy").removeAttribute("disabled");
			encode_output.style["outline"] = "4px solid yellow";
		} else {
			document.getElementById("encode_button_copy").setAttribute("disabled", "");
			encode_output.style["outline"] = "none";
		}
	}

	encode_input.addEventListener("input", encode_input_handler );
}
//Encryption logic for buttons
{
	document.getElementById("encode_button_clear").addEventListener(
		"click",
		function() {
			let encode_input	= document.getElementById("encode_input");
			document.getElementById("encode_input").value = "";
			encode_input.dispatchEvent(event_input);
			encode_input.focus();
		}
	);
	document.getElementById("encode_button_reveal").addEventListener(
		"click",
		function() {
			let encode_output = document.getElementById("encode_output");
			encode_output.value = reveal(encode_output.value);
			document.getElementById("encode_input").focus();
		}
	);
	document.getElementById("encode_button_hide").addEventListener(
		"click",
		function() {
			let encode_output = document.getElementById("encode_output");
			encode_output.value =...