One possibility, take a look:
<script language="javascript" type="text/javascript" src="./jquery-3.1.1.slim.min.js" />
vs
<script language="javascript" type="text/javascript" src="./jquery-3.1.1.slim.min.js"></script>
The first method is actually wrong, however the browser does not complain at all. You need to be sure that you are indeed closing the javascript tag in the proper way.