details

An object with the following properties:

tabId Optional

integer. The tab whose popup to get.

windowId Optional

integer. The windows whose popup to get.

• If windowId and tabId are both supplied, the function fails.
• If windowId and tabId are both omitted, the global popup is returned.

A Promise that will be fulfilled with a string containing the URL for the popup's document. This will be a fully qualified URL, such as moz-extension://d1d8a2eb-fe60-f646-af30-a866c5b39942/popups/popup2.html.

Get the popup's URL:

function gotPopup(popupURL) {
  console.log(popupURL);
}

let gettingPopup = browser.action.getPopup({});
gettingPopup.then(gotPopup);