javascript - Immediately return a resolved promise using AngularJS

Question

I'm trying to get my head around promises in JavaScript (in particular AngularJS).

I have a function in a service, let's call it fooService, that checks if we've loaded some data. If it has, I just want it to return, and if we haven't, we need to load the data and return a promise:

this.update = function(data_loaded) {
    if (data_loaded) return;  // We've loaded the data, no need to update

    var promise = Restangular.all('someBase').customGet('foo/bar').then(function(data) {
        // Do something with the data here
    }

    return promise;
}

I have another function that then calls the update function of fooService like so:

fooService.update(data_loaded).then(function() {
    // Do something here when update is finished
})

My issue here is that if we don't need to load the data in the update function, a promise isn't returned, so the .then() is not called in my other function. What should the approach be here - basically I want to return a resolved promise immediately from the update() function if we do not need to get data from the Restangular call?

Answer 1

As your promise use the same syntax as the JavaScript native one, you could use and return an already resolved JavaScript promise : Promise.resolve()

return(Promise.resolve("MyReturnValue"));