JSFiddle - React, Tailwind, and code Playground

HTML

<input type="button" id="more_fields" onclick="add_fields();" value="Add More" />
<div id="room_fileds">
    <div class='label'>Room 1:</div>
    <div class="content" id="wrapper"> 
        <span>Width: <input type="text" style="width:48px;" name="width[]" value="" /><small>(ft)</small></span>
         <span>Length: <input type="text" style="width:48px;" namae="length[]" value="" /><small>(ft)</small></span>
    </div>
</div>

JavaScript

function add_fields() {
    document.getElementById('wrapper').innerHTML += '<span>Label: <input type="text"><small>(ft)</small></span>\r\n';
}