enhancement: store.subscribe(listener, filter)

[warren-bank]

new (optional) input parameter: filter

• its purpose is to conditionally filter when listener is called
• when its value is:
  • undefined:
    • listener is called as normal
  • function:
    • input: (oldState, newState)
    • output: boolean
      • when truthy, listener is not informed of this state change
  • boolean && true:
    • listener is not informed when newState
      is equal (by reference) to oldState

[warren-bank]

Hi.

I was just thinking..

• maybe the name filter wasn't the absolute best choice?
  • normally, a filter function returns true to include and false to exclude..
    • whereas this is the other way around
  • would ignore or skip be preferable?
  • of course, this is strictly internal..
    • users passing a function into subscribe can call it anything they like..
    • or make it anonymous (for that matter)

Do you have any opinion?

[markerikson]

This is very similar to the frequently-requested idea of having state and/or action passed to listeners, and we have no plans to implement this. If you'd like to do it yourself, you can implement it as a store enhancer.

For more info, see the FAQ entry on why state and action are not passed to subscribers, and the many prior discussions listed in issue #580 .