I ask a similar question here and Darin Dimitrov answer that we can\'t use Url helper like $.ajax({ url: \'@Url.Action(\"Index\")\', . . . in sepa
Use a hidden field to store your url, then use javascript to read the hidden field, then use that in your code. That way you can keep the JS file separate to the view. Something like this:
//In Your View
@Html.Hidden("MyURL", Url.Action("Index"))
//In Your JS
var myUrl = $("#MyURL").val();
$.ajax({ url: myUrl , . . .