I have a simple javascript demo file [demo.js], stored in the [sitecollection]/[site]/SiteAssets/Scripts directory:
<html>
<body>
<script type="text/javascript">
var today = new Date();
document.write("<p> Today is: " + today.toString() + "</p>");
</script>
</body>
</html>
If I put the code into a SEWP, it delivers the defined output. However if I put the link ~/SitesAssets/Scripts/demo.js into the jslink of a task list, nothing is happening. What am I doing wrong? Thank you!