function isProbablyReaderable(doc, options = {}) {
  // For backward compatibility reasons 'options' can either be a configuration object or the function used
  // to determine if a node is visible.
  if (typeof options == "function") {
    options = { visibilityChecker: options };
  }

  var defaultOptions = { minScore: 20, minContentLength: 140, visibilityChecker: isNodeVisible };
  options = Object.assign(defaultOptions, options);

  var nodes = doc.querySelectorAll("p, pre, article");

  // Get <div> nodes which have <br> node(s) and append them into the `nodes` variable.
  // Some articles' DOM structures might look like
  // <div>
  //   Sentences<br>
  //   <br>
  //   Sentences<br>
  // </div>
  var brNodes = doc.querySelectorAll("div > br");
  if (brNodes.length) {
    var set = new Set(nodes);
    [].forEach.call(brNodes, function (node) {
      set.add(node.parentNode);
    });
    nodes = Array.from(set);
  }

  var score = 0;
  // This is a little cheeky, we use the accumulator 'score' to decide what to return from
  // this callback:
  return [].some.call(nodes, function (node) {
    if (!options.visibilityChecker(node)) {
      return false;
    }

    var matchString = node.className + " " + node.id;
    if (REGEXPS.unlikelyCandidates.test(matchString) &&
        !REGEXPS.okMaybeItsACandidate.test(matchString)) {
      return false;
    }

    if (node.matches("li p")) {
      return false;
    }

    var textContentLength = node.textContent.trim().length;
    if (textContentLength < options.minContentLength) {
      return false;
    }

    score += Math.sqrt(textContentLength - options.minContentLength);

    if (score > options.minScore) {
      return true;
    }
    return false;
  });
}
Decides whether or not the document is reader-able without parsing the whole thing.
@param {Object} options Configuration object.
@param {number} [options.minContentLength=140] The minimum node content length used to decide if the document is readerable.
@param {number} [options.minScore=20] The minumum cumulated 'score' used to determine if the document is readerable.
@param {Function} [options.visibilityChecker=isNodeVisible] The function used to determine if a node is visible.
@return {boolean} Whether or not we suspect Readability.parse() will suceeed at returning an article object.