JavaScript NodeIterator whatToShow Property

const root = document.createElement("div");
root.innerHTML = "<span>A</span>";

const it = document.createNodeIterator(
  root,
  NodeFilter.SHOW_ELEMENT,
  { acceptNode: () => NodeFilter.FILTER_ACCEPT }
);

console.log(it.whatToShow === NodeFilter.SHOW_ELEMENT); // true
console.log(it.whatToShow); // 1

const root = document.createElement("div");
root.innerHTML = "<span>Hello</span><span>World</span>";

const itEl = document.createNodeIterator(root, NodeFilter.SHOW_ELEMENT);
const itText = document.createNodeIterator(root, NodeFilter.SHOW_TEXT);

const elements = [];
const texts = [];
let n;
while ((n = itEl.nextNode())) elements.push(n.nodeName);
while ((n = itText.nextNode())) {
  const t = n.nodeValue.trim();
  if (t) texts.push(t);
}

console.log(elements); // ["DIV", "SPAN", "SPAN"]
console.log(texts);    // ["Hello", "World"]

const mask =
  NodeFilter.SHOW_ELEMENT |
  NodeFilter.SHOW_COMMENT |
  NodeFilter.SHOW_TEXT;

const it = document.createNodeIterator(
  document.body,
  mask,
  { acceptNode: () => NodeFilter.FILTER_ACCEPT }
);

console.log(it.whatToShow === mask); // true
console.log((it.whatToShow & NodeFilter.SHOW_COMMENT) !== 0); // true
console.log((it.whatToShow & NodeFilter.SHOW_DOCUMENT) !== 0); // false