title: TypoScript: Check if JS/CSS File is already included
body: <p>anybody knows how to check if a js/css file is already included with typoscript?</p>
  
  <p>Example</p>
  
  <pre><code>[Template_A.ts]
  
  page.includeJS {
    jsfile = fileadmin/Template/js/jquery-1.10.2.min.js
  }
  </code></pre>
  
  <p>now if i got an extension with the same include e.g.</p>
  
  <pre><code>[Extension_A.ts]
  
  page.includeJS {
    jsfile = fileadmin/Template/js/jquery-1.10.2.min.js
  }
  </code></pre>
  
  <p>Is there a way to prevent this kind of <em>double code injection</em>? Maybe i got another Template e.g. Template_B.ts where jquery is not included - than the Extension_A.ts has to include jquery by itself.</p>
  
  <p>Kinldy</p>