title: Why does {{undefined + number}} return number?
body: <p>I'm working on an AngularJS project. I noticed that the following expression returns a number.</p>
  
  <p>In the view, <code>{{undefined + 10}}</code> will output 10.</p>
  
  <p>In JavaScript, <code>undefined + 10</code> will output <strong>NaN</strong>.</p>
  
  <p>Why is this behavior different in a view? </p>