typo3 TypeError: document.getElementById(...) is null code example
Example: javascript typeerror document.getelementbyid(...) is null
This can happen if the JavaScript code is executed before the
page is fully loaded. Try moving the <script> in the HTML
document to the end. For example:
<html>
<body>
// HTML Code
<script src="filename.js"></script>
</body>
</html>