javascript childNodes - how to get values? whi a console.logged value return undefined?

Question

Ciao

i have some xHTML like this:


<!DOCTYPE html>
  <html>
    // [ wellformed xHTML here ] 
  </html>
<!-- a comment here -->`

I would get the text string inside the last comment: "a comment here". Note: it's outside main html tag.

I can log it in console trying: var goal = document.getElementsByTagName('html')[0].parentNode.childNodes; console.log(goal);

... goal.lenght is 3, and finally goal[2] .textContent should contain the string "a comment here",

but i tried yet with .nodeValue, innerHTML etc, also converting to array, and all return undefined...

Shoudl contain _how_? A comment is not really ating like a tag, and it's contents might not be in `.textContent` or `.innerHTML`. — somethinghere, Feb 14 '23 at 14:05
A comment is not processed by the browser and it’s completely anonymous, there is not tag for it, it’s not a child, it’s simply just an invisible message. — Parking Master, Feb 14 '23 at 14:22

score 0 · Accepted Answer · answered Feb 14 '23 at 14:29

Comments are anonymous, you cannot read them anywhere except your code editor, and that’s the whole point.

Aside from comments not being designed to be readable by JavaScript, you can still see them in their parent node’s innerHTML.

A simple way to do this is:

Get the parent HTML code
Parse it and get all of the comments
Return the value so you can use it

Here’s a simple script that will get all of the comments from the entire page:

function filterNone() {
    return NodeFilter.FILTER_ACCEPT;
}

function getAllComments(rootElem) {
  var comments = [];
  // Fourth argument, which is actually obsolete according to the DOM4 standard, is required in IE 11
  var iterator = document.createNodeIterator(rootElem, NodeFilter.SHOW_COMMENT, filterNone, false);
  var curNode;
  while (curNode = iterator.nextNode()) {
    comments.push(curNode.nodeValue);
  }
  return comments;
}

// Wait until the window is done loading
window.addEventListener("load", function() {
  console.log(getAllComments(document.body));
});

Thank you for clarify to me the "problem" with DOM comments, but also your code still to give an empty array — Crxm CrossMedia, Feb 14 '23 at 14:47
work changing getAllComments(document.body) to getAllComments(document)[0] Tnxs so much!! — Crxm CrossMedia, Feb 14 '23 at 15:10

javascript childNodes - how to get values? whi a console.logged value return undefined?

1 Answers1