JSFiddle - React, Tailwind, and code Playground

HTML

<div>
    <div id="foo"></div>
    <div id="bar"></div>
</div>

JavaScript

var e = document.getElementById("bar");
var check = false;
var c = e.parentNode.querySelectorAll('p');
for(var i = 0; i < c.length; i++){
    if (c[i]==e){
        check = true;
    }
}

console.log(check);