javascript error();

Ada yang bisa bantu fix ini masalahnya dimana? padahal sudah benar direktori file nya di load begitu juga codingannya ..

File HTML / Row Up.

 <a href="javascript:atas();" class="arrow-up">↑</a>

==============================================================================

File atas.js

 function atas() {
  $('html, body').animate({
    scrollTop: 0
  }, 1200);
}

==============================================================================

Javascript loader di bagian bawah.

 <script type="text/javascript" src="js/atas.js"></script>
<script type="text/javascript" src="js/jquery.js"></script>
<script type="text/javascript" src="js/bootstrap.min.js"></script>
<script type="text/javascript" src="js/index.js"></script>