onde colocar arquivos JS no Flask
<script src="{{url_for('static', filename='somejavascriptfile.js')}}"></script>
Angry Ant
<script src="{{url_for('static', filename='somejavascriptfile.js')}}"></script>
<script src="{{url_for('static', filename='js/modernizr-2.6.2.min.js')}}"></script>