JSFiddle - React, Tailwind, and code Playground

HTML

<body><div>
    <button  class="btn">BUTTON</button>
</div></body>
<button id="test">is button in document</button>

JavaScript

var btn = $('.btn');

btn.click(function(){
   btn.remove().wrap('<body/>'); 
});

$('#test').click(function(){
   alert(isInDom(btn));
});
    
    
function isInDom(obj) {
    var someBody =obj.parents('body');
    return someBody.length > 0 && someBody.get(0) === document.body;
}