How does it work?

The three objects dispatches, commits, getters are Proxy objects. So when you are trying to access a module store:

dispatches.count;

it is impossible to check dynamically if the count module exists on the Vuex store. We can, but we would need to access the private methods on the root store, that wouldn't be a good idea. It is up to you to make sure you are accessing a module that exists on the Vuex store (perfect to write tests!). And an ide_helper is on my to do list, so the autocomplete would to avoid typos.

To add, in the example above, dispatches captures the first argument count as the module you are wishing to access its methods, then returns another Proxy object. Its implementation will check the next accessed property and will translate it to store.dispath(). For example, if we will access dispatches.count.increment(), this will become:

$store.dispatches('count/increment', ...args);

where ...args are any arguments passed to dispatches.count.increment() if any.

It is the same as for the commits and getters objects.

commits.<module>.<method>

getters.<module>.<property>

will be translated to:

$store.commits('module/method')

$store.getters['module/property']