Can't get Edge to Return a Promise in my WebExtension

问题

I am trying to create a new tab using browser.tabs.create() from my background.js WebExtension as shown here:

createTab: function () {
    var newTab = browser.tabs.create({ url: someUrl });
    newTab.then(onCreated, onError);
}

The new tab creates in the browser, but when the last line is reached, an error is thrown:

SCRIPT5007: Unable to get property 'then' of undefined or null reference

The Locals window shows newTab is undefined.

What am I doing wrong here? I thought that .create() would immediately return a Promise. I know create() is an asynchronous function - but my calling function doesn't need to by async, does it?

Any help would be appreciated.

回答1:

I ended up reading the Microsoft documentation (who knew?) and came across this little gem:

Seems pretty definitive; now I just need an example of using callbacks for it instead...

回答2:

As Scott Baker already mentioned, Microsoft Edge extension APIs sadly don't support promises.

So you could refer to this MDN example on how to use callbacks:

browser.windows.onCreated.addListener((tab) => {
  console.log("New tab: " + tab.id);
});

---

Or even better: Provide the callback directly as second parameter to the create function:

var newTab = browser.tabs.create({ url: someUrl }, (tab) => {
  console.log("New window: " + window.id);
});

See the chrome docs (seems to apply for Edge, too): https://developer.chrome.com/extensions/tabs#method-create

Please note: You can achieve the same, if you're aiming for a new window (instead of a new tab) with windows.create(object createData, function callback)

来源：https://stackoverflow.com/questions/47545719/cant-get-edge-to-return-a-promise-in-my-webextension