Like clojure.core/atom, except that it keeps track of derefs.

Creates a Reaction from a function.

- :auto-run - starts running the reaction immediately, and runs again when
atoms deferenced in the function change.
- :on-set - runs when reaction value is updated, before notifying watchers.
- :on-dispose - runs when the reaction is disposed.

Prefer using reagent.core/reaction.

Prefer using reagent.core/reaction.

Creates a Reaction from the body, and runs the body immediately
and again whenever atoms deferenced in the body
change. Body should side effect.

Use dispose! to stop running the Reaction.

Creates a Reaction from the body, and runs the body immediately
and again whenever atoms deferenced in the body
change. Body should side effect.

Use dispose! to stop running the Reaction.

Evaluates `f` and returns the result.  If `f` calls `deref` on any ratoms,
creates a new Reaction that watches those atoms and calls `run` whenever
any of those watched ratoms change.  Also, the new reaction is added to
list of 'watches' of each of the ratoms. The `run` parameter is a function
that should expect one argument.  It is passed `obj` when run.  The `opts`
are any options accepted by a Reaction and will be set on the newly created
Reaction. Sets the newly created Reaction to the `key` on `obj`.