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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