simplify multipart example, add some comments

Author: jonathanong

.jshintignore

@@ -0,0 +1,2 @@
+node_modules
+*/test.js

body-parsing/app.js

@@ -1,3 +1,13 @@
+/**
+ * Example for handling JSON and urlencoded request bodies.
+ * All the throws at the beginning of the middleware are all app-dependent and may not be suited for your use-case.
+ * For the actual body parsing (yield rawBody and down),
+ * you most may be interested in modules that already do this for you:
+ *
+ * - [body](https://github.com/raynos/body)
+ * - [co-body](https://github.com/visionmedia/co-body)
+ */
+
 var koa = require('koa');
 var qs = require('querystring');
 var rawBody = require('raw-body');

flash-messages/app.js

@@ -1,3 +1,8 @@
+/**
+ * A very simple flash example.
+ * Only uses JSON for simplicity.
+ */
+
 var koa = require('koa');
 var rawBody = require('raw-body');
 var session = require('koa-session');

multipart/app.js

@@ -1,44 +1,51 @@
+/**
+ * Multipart example downloading all the files to disk using co-busboy.
+ * If all you want is to download the files to a temporary folder,
+ * just use https://github.com/cojs/multipart instead of copying this code
+ * as it handles file descriptor limits whereas this does not.
+ */
+
 var os = require('os');
 var path = require('path');
 var fs = require('fs');
 var koa = require('koa');
 var parse = require('co-busboy');
 var saveTo = require('save-to');
-var archan = require('archan');
 
 var app = module.exports = koa();
 
 app.use(function *(){
-  // create a go-like channel for control flow
-  var ch = archan({
-    concurrency: 1 // save only 1 file at a time
-  });
-
   // parse the multipart body
   var parts = parse(this, {
     autoFields: true // saves the fields to parts.field(s)
   });
 
   // create a temporary folder to store files
-  var tmpdir = path.join(os.tmpdir(), Math.random().toString(36).slice(2));
+  var tmpdir = path.join(os.tmpdir(), uid());
 
   // make the temporary directory
   yield fs.mkdir.bind(null, tmpdir);
 
+  // list of all the files
+  var files = [];
+  var file;
+
   // yield each part as a stream
   var part;
   while (part = yield parts) {
-    // wait if there are too many file descriptors opened
-    yield* ch.drain();
-    // save each part to a file,
-    // but do it in a different channel
-    // so we don't block this particular while loop.
-    saveTo(part, path.join(tmpdir, part.filename), ch.push());
+    // filename for this part
+    files.push(file = path.join(tmpdir, part.filename))
+    // save the file
+    yield saveTo(part, file);
   }
 
   // return all the filenames as an array
   // after all the files have finished downloading
-  this.body = yield* ch.flush();
+  this.body = files;
 })
 
-if (!module.parent) app.listen(3000);
+if (!module.parent) app.listen(3000);
+
+function uid() {
+  return Math.random().toString(36).slice(2);
+}

package.json

@@ -9,7 +9,6 @@
     "koa-session": "koajs/session",
     "co-busboy": "cojs/busboy",
     "save-to": "~1.0.0",
-    "archan": "~0.4.0",
     "raw-body": "~1.1.1"
   },
   "devDependencies": {