title: How to use channel.assertQueue function from amqplib library for node.JS?
body: <p>I am developing a messaging app using RabbitMQ, and Node.JS. I am using amqplib for this purpose. I am new to Node.JS and finding few difficulties in understanding the syntax of amqplib..
  For e.g. there is a function for declaring queue,
  that is</p>
  
  <pre><code>channel.assertQueue([queue, [options, [function(err, ok) {...}]]]);
  </code></pre>
  
  <p>I have been referring <a href="http://www.squaremobius.net/amqp.node/doc/channel_api.html" rel="noreferrer">This</a> from last 2-3 days but still I am not clear about  these -> <code>err</code> and <code>ok</code>. How to use these parameters?</p>
  
  <p>An example would be much much appreciated.</p>