title: Javascript object is not function
body: <p>I'm new to Javascript and am confused about the error messages I get:</p>
  
  <p>I have the JavaScript Code:</p>
  
  <pre><code>function tile(x,y) {
  return ((worldw * y) + x);
  }
  
  alert(tile(5,5));
  </code></pre>
  
  <p>But I get the error message in Chrome that "Object is not a function".</p>
  
  <p>How can I fix this and what does the error message mean?</p>