Hi Jorge,
Yes, this is just the way things are in node.
I would probably do it slightly differently, as you suggest, with an API
that lets you read the prime numbers one by one:
var nextPrime = primeGenerator.create();
nextPrime(cb);
State encapsulated in a closure rather than an object. I like that.
Bruno
On Saturday, April 28, 2012 12:04:28 PM UTC+2, Jorge wrote:
>
> Hi Bruno,
>
> On Apr 28, 2012, at 11:14 AM, Bruno Jouhier wrote:
>
> > Neither!
> >
> > I think that question should be callbacks vs. events vs. streams:
> > • Callback: called only once, when the function is done, to
> return result (optional) or error.
> > • Event: called repeatedly by the function to notify its
> listeners. Can be used to send intermediate results as they come.
> > • Stream: higher level concept based on events, with
> standardized event types (data, end, error, drain) and standardized API
> (pause, resume, write, ..).
> > So, assuming prime computation is asynchronous:
> >
> > • If the function computes the N first primes and returns them
> all at once, it should use a callback.
> > • If the function returns the primes one by one, it should use
> events. It may also use a stream but that seems a bit over-engineered.
>
>
> Good, yes, that's the way it is in node, but it does not explain *why* it
> is so.
>
> .readFile() could as well deliver the chunks to the cb as they're read
> from disk, and to use it you'd need to write just one line:
>
> fs.readFile(path, cb);
>
> While to do the same with an evented interface there's a lot of
> boilerplate to write, and an extra object to create:
>
> reader= new fileReaderConstructor(path);
> reader.on('data', cb);
> reader.on('end', endCB);
> reader.on('error', errorCB);
>
> It seems to me that the former is more functional and makes good use of
> closures (*), while the latter is the approach a classic OOP programmer
> would tend to write instead.
>
> (*)In JavaScript we don't need to create objects to save state.
> --
> Jorge.
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