JSFiddle - React, Tailwind, and code Playground

HTML

<input type="radio" name="group">
<input type="radio" name="group">

<textarea placeholder="Окно ввода для первой radio кнопки"></textarea>
<textarea placeholder="Окно ввода для второй radio кнопки"></textarea>

JavaScript

var textarea = [].slice.call(document.querySelectorAll('textarea'));
[].forEach.call(document.querySelectorAll('[type=radio]'), function(el, i) {
    (function(index) {
    	textarea[index].style.display = el.checked ? 'inline' : 'none';
        el.addEventListener('change', function() {
        	textarea.forEach(function(ta, i){
            	ta.style.display = i === index ? 'inline' : 'none';
            });
        });
    }(i));
});