JSFiddle - React, Tailwind, and code Playground

HTML

<div>
    <h1 id="top">Selector Test Kit</h1>
    <textarea id="domain" name="domain">&lt;body&gt;&lt;p&gt;Paragraph Here&lt;/p&gt;&lt;/body&gt;</textarea>
    <input type="text" id="selector" name="selector" value="p" />
    <p>Target: <span id="target"></span></p>
</div>

CSS

#top { margin-bottom: 10px; font-size: 150%; font-weight: bold; }
#target { color: #f00; cursor: pointer; }
#domain { width: 400px; }
#selector { width: 400px; clear: both; margin-bottom: 10px; }

JavaScript

$('#domain,#selector').change(function() {
    var textContent = $($('#selector').val(), '<div>' + $('#domain').val() + '</div>').text();

    if (textContent == '') {
        textContent = '« not found »';
    }

    $('#target').text(textContent);
}).keyup(function() {
    $(this).change();
}).change();