Node.isEqualNode()

var isEqualNode = node.isEqualNode(otherNode);

<div>This is the first element.</div>
<div>This is the second element.</div>
<div>This is the first element.</div>
<p id="output"></p>

#output {
  width: 440px;
  border: 2px solid black;
  border-radius: 5px;
  padding: 10px;
  margin-top: 20px;
  display: block;
}

let output = document.getElementById("output");
let divList = document.getElementsByTagName("div");
output.innerHTML +=
  "div 0 equals div 0: " + divList[0].isEqualNode(divList[0]) + "<br/>";
output.innerHTML +=
  "div 0 equals div 1: " + divList[0].isEqualNode(divList[1]) + "<br/>";
output.innerHTML +=
  "div 0 equals div 2: " + divList[0].isEqualNode(divList[2]) + "<br/>";