From c7c22e3db1c826bcfb2bc66651ec480aae0d4ae0 Mon Sep 17 00:00:00 2001
From: yo mama <pepper@scannerjammer.com>
Date: Sat, 4 Apr 2015 01:00:59 -0700
Subject: first

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+## Sending events both ways between the main thread and a worker thread
+
+This third example demonstrates how we can use events to communicate in both directions
+between main thread and worker thread.
+
+Like before, we create a worker thread and we define the fibonacci function:
+
+``` javascript
+var Threads = require('webworker-threads');
+var t = Threads.create();
+
+function fibo(n) {
+	return n > 1 ? fibo(n - 1) + fibo(n - 2) : 1;
+}
+```
+
+In the previous example we were running a loop that generates fibonacci numbers in the worker thread.  
+This is fine if the generator produces the number at a slower rate than the main thread can consume them 
+but it will hog memory if the main thread is too busy and cannot consume the data events fast enough.  
+We can improve this by controlling the flow with events in both directions.
+
+The `thread` global variable that **webworker-threads** predefines in every worker thread is also an `EventEmitter`.  
+So we will use it to send events in the other direction, from the main thread to the worker thread.
+
+Our modified generator does not use a loop any more. Instead, it generates numbers in response to `next` events
+sent from the main thread. Here is the new generator:
+
+``` javascript
+function generateFibos() {
+	var i = 1;
+	thread.on('next', function() {
+		thread.emit('data', i, fibo(i));
+		i++;
+	});
+}
+```
+
+From the main thread, we listen for the `data` events emitted by the worker thread.  
+Every time we get a `data` event from the worker thread, we print the result and we `emit` a 
+`next` event into the worker thread (stopping at 40): 
+
+``` javascript
+t.on('data', function(n, result) {
+	console.log('fibo(' + n + ') = ' + result);
+	if (n < 40) t.emit('next');
+	else console.log('bye!'), t.destroy();
+});
+```
+
+We now have all we need for our little ping-pong game. We load the two functions into the thread:
+
+``` javascript
+t.eval(fibo);
+t.eval(generateFibos);
+```
+
+We start the generator in the worker thread:
+
+``` javascript
+t.eval("generateFibos()");
+```
+
+And we start the game by emitting the first `next` event:
+
+``` javascript
+t.emit('next');
+```
+
+### Output
+
+```
+fibo(1) = 1
+fibo(2) = 2
+fibo(3) = 3
+fibo(4) = 5
+...
+fibo(39) = 102334155
+fibo(40) = 165580141
+bye!
+```
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