title: Definition vs initialization
body: <p>What's the difference between declaration, definition and initialization? Example:</p>
  
  <pre><code>// Is this a declaration?
  var foo;
  
  // Did I defined object in here (but it is empty)?
  var foo = {};
  
  // Now that object is initialized with some value?
  var foo = {first:"number_one"};
  </code></pre>