So I have this question about $ sign suffix naming convention in the RxJs code and Angular specifically. In angular best practices documentation and in the overall I have found that we should use it when declaring the Observable, but haven't seen using it with Subjects. Why ? I thought it should mean "asynchronous". Moreover Subjects are Observables. So they are async and you have to subscribe to them. For now I started using $ with Subjects too. Is any real con of this practice ?
Santiago Trujillo
On top of what Stoobish and Nipuna have said, I'd add that I like to have a $ as suffix as well to avoid ending up with a same variable name when working with an extracted value from a stream.
For example:
const currentTimeSeconds = currentTimeMs.pipe(
map(currentTimeMs => currentTimeMs * 1000)
)
In the example above you'd end up with 2 variables named currentTimeMs. Sure that'd still work, but it's more confusing than helping. Sure you can rename the inner variable to something different as well. But overall I find it much clearer to have the following instead
const currentTimeSeconds$ = currentTimeMs$.pipe(
map(currentTimeMs => currentTimeMs * 1000)
)
Every subject is an observable.
If you look at Angular docs:
This can be useful when scanning through code and looking for observable values. Also, if you want a property to store the most recent value from an observable, it can be convenient to use the same name with or without the “$”.
The $ sign suffix doesn't mean asynchronous, its used as a soft convention to indicate that the variable is a stream. It is more like a naming helper to indicate types.