I'm certainly no expert, but I expect the design choice was made to do it
that way to make the C/C++ asynchronous calls within the node core to be
simpler and easier. At present, to jump back into the callback the C++ side
just needs a single function reference. If a list of arbitrary arguments
are also allowed then these would also have to handled and tracked in the
C++ code - not too difficult, but extra work nonetheless. So the current
mechanism gives a cleaner separation between the Javascript and C++ worlds.
There is also the issue that the extra arguments will make it very
difficult for the node api to have functions with optional arguments.
On 12 December 2012 11:53, Michael Hasenstein <hasenst...@yahoo.com> wrote:
> I know how I can do it (at least 3 different very ways came to my mind
> immediately), I said so ;-) - that was't my question (or point).
>
> I don't WANT to have to write that, if I can help it.
>
> I would except the explanation that since node.js is very low-level
> burdening the API functions with an additional 'if' to make it call
> the callback with *optional* (that's what leads to the 'if')
> parameters given to it for that purpose, and since the API functions
> are possibly called millions of times per second, the decision was
> made to burden the code using node.js instead of node.js.
>
>
>
>
> On Wed, Dec 12, 2012 at 12:47 PM, Jonathan Dickinson
> <jonathand...@gmail.com> wrote:
> > You can do it with .bind(). I assume that the 1...n arguments of .bind()
> are
> > often overlooked.
> >
> > var fs = require('fs');
> >
> > function onStat(file, err, stat) {
> > if (stat.isFile()) {
> > //fs.readFile(...)... WHICH FILE????
> > console.log(file); // This file
> > }
> > }
> >
> > var files = [
> > "E:\\site.css",
> > "E:\\stacks.txt",
> > "E:\\Node",
> > ];
> >
> > files.forEach(function (file) {
> > fs.stat(file, onStat.bind(this, file));
> > });
> >
> > On Wednesday, 12 December 2012 11:36:29 UTC+2, Michael Hasenstein wrote:
> >>
> >> This is not a technical question (I'm quite clear about how the stuff
> >> works). I also did some (Google) research before asking.
> >>
> >> I'm just curious if there is a good reason that I just fail to see... I
> AM
> >> aware that very obviously I am not the first person to think about
> this, but
> >> I just could not find ANY good explanation for the "WHY".
> >>
> >> Let me just give an example.
> >>
> >> I get an array of strings (filenames, e.g. from fs.readDir), and now I
> >> want to process them: fs.stat(), fs.readFile(), then minify, then
> >> fs.writeFile().
> >>
> >> now. all those operations are asynchronous unless I use the sync-version
> >> of those functions.
> >>
> >> PROBLEM:
> >>
> >> I really, really, REALLY need that filename string it all started with
> in
> >> the other functions - so now, with node.js callback API being as it is,
> I
> >> have to write code that I really, REALLY dislike, because it seems
> >> suboptimal compared to what I COULD do.
> >>
> >> What I COULD do but which the node.js callbacks don't allow is the
> passing
> >> of additional parameters to my callback.
> >>
> >> Code:
> >> function onStat(err, stat) {
> >> if (stat.isFile()) {
> >> //fs.readFile(...)... WHICH FILE????
> >> }
> >> }
> >>
> >> files.forEach(function (file) {
> >> fs.stat(<some path> + file), onStat);
> >> });
> >>
> >> I AM AWARE HOW TO SOLVE THIS. Pls. don't reply showing me how I can
> easily
> >> solve this with additional function scopes.
> >>
> >> My issue with adding additional functions is that that solution SUCKS.
> If
> >> I could just add additional parameters to the fs.stat() call which my
> >> callback gets as 3rd, 4th, etc parameter (or an array or an object,
> >> whatever) the sun would still shine.
> >>
> >> However, node.js makes me add additional quite useless scopes.
> >> ALTERNATIVELY I write all those callback functions into the lexical
> scope of
> >> the forEach() - that's what has been called "callback hell" for a long
> time
> >> - no way.
> >>
> >> So, can anyone enlighten me - and I MAY INDEED be simply incredibly
> stupid
> >> not to see the point without help - why node.js could not just let me
> add
> >> custom parameters for callbacks? Again: additional scope-producing
> functions
> >> are NOT OPTIMAL IMHO - it produces overhead both in the code and during
> >> runtime. There MUST be a reason, otherwise by now, node.js almost at
> version
> >> 0.9, would have been changed, wouldn't it? I mean, libraries like YUI3
> give
> >> me the option to add my own custom parameters to be passed down to
> callback
> >> functions, to solve this exact problem.
> >>
> >> TIA!
> >>
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