In your case you need to pass urls to js code files from views with using url helpers. Modify your js files to use one of module pattern.
First way - importing of global variables:
js
(function (url) {
// your code
}(external_url));
view
<script type="text/javascript">
var external_url = '@Url.Action("action", "controller")'; // define global variable `external_url` with helper. This should be defined before script run.
</script>
<script type="text/javascript" src="jsfile.js" />
Second way - exporting module:
var module = (function (url) {
// your code
}(external_url));
view
<script type="text/javascript" src="jsfile.js" />
<script type="text/javascript">
module('@Url.Action("action", "controller")');
</script>