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    <p>What you miss is that JavaScript isn't asynchronous at all! What I mean is that JavaScript is single-threaded and asynchronous operations are actually not asynochronous. There is a very fancy queue model which gives as the illusion of JavaScript being asynchronous (don't get me wrong: it still <strong>is</strong> the most efficient model).</p> <p>So what does it mean? It means that once the synchronous code is running <strong>it is impossible</strong> for other code to be running parallely. So for example in this code</p> <pre><code>var req = http.request(options); req.end(); req.on(...); </code></pre> <p>the request is scheduled, but the main thread (i.e. the operation) hasn't ended at <code>req.end()</code>. As long as the main operation has not finished no asynchronous code can fire in-between. In particular the handler is <strong>always</strong> set before the actual event has any chance to occure.</p> <p>One more example to make it a bit clearer. Consider this code:</p> <pre><code>var http = require('http'); http.createServer(function (req, res) { res.writeHead(200, {'Content-Type': 'text/plain'}); res.end('Hello World\n'); while(true) { } // &lt;------ infinite loop doing nothing }).listen(1337, '127.0.0.1'); </code></pre> <p>Note that the first request will finish with success. But any other request will <strong>never</strong> get a response. This is because the loop will never finish the operation and JavaScript <strong>cannot</strong> jump to another event because of it. This code permamently crashes the app beyond any hope. So be careful with synchronous code with Node.js. :)</p>
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    1. COI assume then that declaring an event handler with .on() is synchronous, then? Otherwise, the assignment would be added to the queue after the request and end.
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    2. CO@Aejay Yes, it is synchronous.
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