Creates an observer from the given function. An observer
is like a reactive function in that it can read reactive
values and call reactive functions, and will
automatically re-execute when those dependencies change.
But unlike reactive functions, it doesn't yield a result
and can't be used as an input to other reactive
functions. Thus, observers are only useful for their side
effects (for example, performing I/O).
Usage
observe(func)
Arguments
func
The function to observe. It must not have any
parameters. Any return value from this function will be
ignored.
Details
Another contrast between reactive functions and observers
is their execution strategy. Reactive functions use lazy
evaluation; that is, when their dependencies change, they
don't re-execute right away but rather wait until they
are called by someone else. Indeed, if they are not
called then they will never re-execute. In contrast,
observers use eager evaluation; as soon as their
dependencies change, they schedule themselves to
re-execute.