StackOverflow #38155218

HTML

<div id="dTest"></div>

JavaScript

var div=document.getElementById("dTest");
var shadow=div.createShadowRoot();
shadow.innerHTML='<p>Hi!</p>';
document.body.appendChild(document.createTextNode(shadow.childNodes.length));
console.log(shadow.querySelectorAll("p"));
console.log($("p",shadow));
$("p",shadow).html("Hello!");