Why do you execute $ q.when () without passing a promise / value to it?

Question

According to Angular docs in $ q , $ q.when () is expecting a promise / value to be passed.

But I just came across another code where it called without passing any parameters. Here is a simplified version of what I see:

var modal = false; if (modalOpen) { return $q.when() } modalOpen = true; modal = newModal({ template: opts.template, }); modal.result.finally(function(){ modalOpen = false; }); } 

Answer 1

Methods must either return synchronously or return asynchronously to remain consistent. If the method sometimes returns synchronously and still wants to save the fact, then it is already resolved transparently - it returns an empty resolved promise. Having an API that sometimes returns promises, and sometimes synchronously, is a recipe for problems .

Using $q.when is the easiest way to get an empty resolved promise in Angular.