forEach method of Node.childNodes?

Question

After providing an incorrect answer concerning the .item() property of Node.childNodes for a question, I inspected __proto__ of the returned childNodes of a form element and found a forEach method.

The forEach method of Node.childNodes is not documented in the specification of NodeList, in Methods at MDN, or Interface NodeList, and does not appear to be mentioned in Iterate a NodeList using forEach method or pages linked to that Question; though it appears available in Chromium 50.

Is the method available only at relatively recent versions of Chrome / Chromium? If yes, is this documented?

Is there any documentation concerning the forEach() method of Node.childNodes?

---

document.querySelector("form").addEventListener("submit", function(e) {
  e.preventDefault();
  var form = e.target;
  form.childNodes.forEach(function(el) {
    if (el.tagName === "INPUT" && el.type !== "submit")
      snippet.log("name:" + el.name + ", value:" + el.value)
  });
});

<form>
  <input type="text" name="firstName" value="The first name">
  <input type="text" name="lastName" value="The last name">
  <input type="email" name="emailAddress" value="[email protected]">
  <br>
  <input type="submit" value="Submit">
</form>
<!-- Script provides the `snippet` object, see http://meta.stackexchange.com/a/242144/134069 -->
<script src="//tjcrowder.github.io/simple-snippets-console/snippet.js"></script>

Answer 1

DOM4 now defines NodeList as an iterable:

iterable<Node>;

According to the IDL draft, that means

An interface can be declared to be iterable by using an iterable declaration (matching Iterable) in the body of the interface.

iterable<value-type>;
iterable<key-type, value-type>;

Objects implementing an interface that is declared to be iterable support being iterated over to obtain a sequence of values.

Note: In the ECMAScript language binding, an interface that is iterable will have “entries”, “forEach”, “keys”, “values” and @@iterator properties on its interface prototype object.

If a single type parameter is given, then the interface has a value iterator and provides values of the specified type.