title: how to detect a function was called with javascript
body: <p>I have a javascript function.</p>
  
  <p>How to check:</p>
  
  <ul>
  <li><p>if function was called ( in <code>&lt;head&gt;&lt;/head&gt;</code> section have this function), then not to call the function</p></li>
  <li><p>if function was not called ( in <code>&lt;head&gt;&lt;/head&gt;</code> section haven't this function), then call the function</p></li>
  </ul>
  
  <p>like <code>require_once</code> or <code>include_once</code> with <strong>PHP</strong></p>