new author, new article, Sequential programming for Node.js

articles/sequential-programming-for-node.js.markdown

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+Wait.for
+=======
+
+Node.js unavoidable style is to make everything that could **even begin to think about blocking** into an async function. 
+This is a core node trait. You can't avoid it, you can't side-step it, Node will not forgive you.  
+
+But... wouldn't be great to be able to call all this great async functions in a sequential/sync mode when the need arises? 
+
+Specially the need not to fall into callback hell?
+
+I believe async is great, and obviouslly there are no other way to program blocking or long-running functions in Node. 
+But sometimes, when you're coding business DB access logic, as example, 
+a sync-non blocking mode to call asnyc functions is very handy.
+
+That's why I've developed a very small, simple lib called ***wait.for***, -I mean ***simple***, not future promises, I mean ***simple*** now. - ;)
+
+Wait.for, as it name imples, bassically provides the programmer with a ***wait.for*** function.
+
+What does wait.for does?
+--
+
+wait.for waits for the async function to callback, before continuing to the next line, and it does it WITHOUT blocking node.
+
+I've developed two versions of ***Wait.for*** based on different thechonolgies under the hood.
+
+* one is [wait.for based on node-fibers](https://github.com/luciotato/waitfor) (github repo)
+
+* other is [wait.for based in the upcoming ES6-Harmony generators](https://github.com/luciotato/waitfor-ES6) (github repo)
+
+I've coded [wait.for based on node-fibers](https://github.com/luciotato/waitfor), two weeks ago. 
+After publishing it, several people ask me: "why not base it on ES6-Harmony generators?". So I started looking for information on such a migration. 
+After a quick search, the migration did not seem possible:
+(According to this: http://stackoverflow.com/questions/18293563/can-node-fibers-be-implemented-using-es6-generators
+and this: http://calculist.org/blog/2011/12/14/why-coroutines-wont-work-on-the-web)
+
+However, the basic building blocks of ES6 generators are the same for the concept of fibers, 
+so I started trying to port **wait.for** to ES6...
+
+It didn't looked good, ***but it went much better than expected!***
+
+***The funny thing is***, the implementation of the core function ***wait.for(async,arg...)***, using ES6 generators is:
+
+```javascript
+wait.for = function( asyncFn ) { return arguments; }
+```
+Yes, just return arguments.
+
+Compare it to **wait.for** based on node-fibers:
+
+```javascript
+wait.for = function(asyncFn){ 
+        var newargs=Array.prototype.slice.call(arguments,1); // remove function from args
+        return Wait.applyAndWait(null,fn,newargs); 
+    }
+```
+
+**wait.for** based on node-fibers *actually does something*: calls ***Wait.applyAndWait***, which in turn uses node-fibers to handle the async call. 
+
+In contrast ES6 based implementation of **wait.for(asyncFn)** does basically nothing 
+(the magic control flow resides in ***yield***)
+
+You can use ***wait.for*** inside a generator (function*) in conjunction with new JS/ES6 ***yield*** keyword, as in:
+
+```javascript
+var data = yield wait.for ( fs.readFile, '/etc/somefile' );
+```
+
+<h2>Surprisingly, ES6 generators-based implementation of <i>function wait.for(asyncFn)</i> 
+is almost a no-op, you can even completely omit it calling it...</h2></blockquote>
+
+Given that evaluating ***wait.for*** return its arguments, the call can be replaced with an object literal, which is an array-like object. It results that:
+```javascript
+
+wait.for( asyncFn, arg1, arg2 )  // return arguments
+=== {0:asyncFn, 1:arg1, 2:arg2 } // is equivalent to...
+~= [ asyncFn, arg1, arg2 ] // is similar to...
+```
+so, the following two snippets are equivalent (inside a generator launched via ***wait.launchFiber(generator)***):
+
+```javascript
+// call an async function and wait for results, (wait.for syntax):
+console.log( yield wait.for ( fs.readFile, '/etc/somefile', 'utf8' ) );
+
+// call an async function and wait for results, (fancy syntax):
+console.log( yield [ fs.readFile, '/etc/passwd', 'utf8' ] );
+```
+
+Check both repositories:
+
+* [wait.for based on node-fibers](https://github.com/luciotato/waitfor) 
+
+* [wait.for based in the upcoming ES6-Harmony generators](https://github.com/luciotato/waitfor-ES6)
+
+
+Advantages of wait.for
+---
+
+* Avoid callback hell / pyramid of doom
+* Simpler, sequential programming when required, without blocking node's event loop (thanks to fibers)
+* Simpler, try-catch exception programming. (default callback handler is: if (err) throw err; else return data)
+* You can also launch multiple parallel non-concurrent fibers.
+* No multi-threaded debugging nightmares, only one fiber running at a given time (thanks to fibers)
+* Can use any node-standard async function with callback(err,data) as last parameter.
+* Plays along with node programming style. Write your async functions with callback(err,data), but use them in sequential/SYNC mode when required.
+* Plays along with node cluster. You design for one thread/processor, then scale with cluster on multicores.

authors/Lucio M. Tato.markdown

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+Github:   luciotato
+Email:    [email protected]
+Company: http://tecnogob.com/
+Consulting: http://prosart.com/
+Location: Pilar, Buenos Aires, Argentina
+
+I've started programming at age 12, even before owning a computer. My first computer was a ZX-Spectrum. I've programmed
+from Z80 assembly and x86 assembly years ago to .NET and node.js today, with everything in between.
+I own a company which provides services to country governments and large organizations in Argentina, also I'm on the board
+of Prosart Development Studio, also located in Argentina, specialized in tackling challenging projects.