Crash when XHR request fails and no fail handler is defined

[danports]

If an XHR request fails without a defined fail handler, the following error is thrown:
fail is not a function

It looks like the XHR failure code doesn't check whether fail is actually defined in the settings object:

bootstrap-autocomplete/src/resolvers.ts

Line 79 in d9701bf

this._settings?.fail(err);

That will check if _settings exists, but not whether fail is defined on that object. A more correct version (we can assume _settings exists here since it has a url we've already requested): this._settings.fail?.(err);

[4braincells]

this._settings?.fail(err);
is the same as
this._settings && this._settings.fail(err);
but not
this._settings.fail && this._settings.fail(err);

in my case, _settings is defined, not fail, so this will throw an exception.
As settings is also optional, it should be

this.jqXHR.fail((err) => {
  console.error(err);
  this._settings && this._settings.fail &&  this._settings.fail(err);
  // or this._settings?.fail?.(err);
});

(as already said by danports) or some more elegant version of this :-p
thus preventing the exception to be thrown.