Simple browser xpath helpers

gistfile1.txt

function* xpathLazy(q) {
  const x = document.evaluate(
    q,
    document,
    null,
    XPathResult.UNORDERED_NODE_ITERATOR_TYPE,
    null
  );
  let n = x.iterateNext();
  while (n) {
    yield n;
    n = x.iterateNext();
  }
}
function xpath(q) {
  const all = [...xpathLazy(q)];
  return all.length > 0 ? all : null;
}
function lookup(sel) {
  if (sel[0] === '/') {
    const els = xpath(sel);
    return els ? els[0] : null;
  } else {
    return document.querySelector(sel);
  }
}