The nodeValue property of the Node interface returns or sets the value of the current node.

A string containing the value of the current node, if any. For the document itself, nodeValue returns null. For text, comment, and CDATA nodes, nodeValue returns the content of the node. For attribute nodes, the value of the attribute is returned.

The following table shows the return values for different types of nodes.

<div id="d1">Hello world</div>
<!-- Example of comment -->
<output id="result">Not calculated yet.</output>

and the following script:

let node = document.querySelector("body").firstChild;
let result = "<br/>Node names are:<br/>";
while (node) {
  result += `Value of ${node.nodeName}: ${node.nodeValue}<br/>`;
  node = node.nextSibling;
}

const output = document.getElementById("result");
output.innerHTML = result;