title: Get sheets with several
body: <pre><code>var spreadsheet = SpreadsheetApp.getActiveSpreadsheet();
  var numsheets = spreadsheet.getNumSheets();
  var sheets = spreadsheet.getSheets()[numsheets];
  </code></pre>
  
  <p>sheets return undefined. </p>
  
  <p>How pass variable as parameter in the []?</p>