Function onDocumentState

src/core/document/ready.js:40–56

* Calls the callback when document's state satisfies the stateFn. * @param {Document} doc * @param {function(Document):boolean} stateFn * @param {function(Document):void} callback

(doc, stateFn, callback)

 * @param {function(Document):void} callback
 */
function onDocumentState(doc, stateFn, callback) {
  let ready = stateFn(doc);
  if (ready) {
    callback(doc);
  } else {
    const readyListener = () => {
      if (stateFn(doc)) {
        if (!ready) {
          ready = true;
          callback(doc);
        }
        doc.removeEventListener('readystatechange', readyListener);
      }
    };
    doc.addEventListener('readystatechange', readyListener);
  }
}

/**
 * Returns a promise that is resolved when document is ready.