ES6中的Angular中的$ q或Promises

Question

I have a project using ES6 and AngularJS, and as far as I found, AngularJS $q promises is synchronous but ES6 promises not. Right? The question is, what are the differences? and when should I use $q or ES6? I know what is the difference between Synchronous and Asynchronous, but got confused between new Promise and AngularJS $q .

raise from here

Answer 1

The statement about $q synchronicity applies to unit tests with ngMock in the first place.

$q promises are capable of being synchronous in production:

let foo;

$q.resolve().then(() => { foo = 1 });
$rootScope.$digest();
console.log(foo === 1);

And they are supposed to be synchronous in unit tests, because all AngularJS services that are responsible for asynchronous behaviour ( $timeout , $http , etc) are mocked with ngMock in order to make tests fully synchronous:

it('...', inject(($q) => {
    let foo;

    $q.resolve().then(() => { foo = 1 });
    $rootScope.$digest();
    expect(foo).toBe(1);
}));

While ES6 promises are asynchronous by design, and then callback runs on next tick:

it('...', (done) => {
    let foo;

    Promise.resolve(1).then(() => {
      foo = 1;
      expect(foo).toBe(1);
    })
    .then(done, done.fail);
});