You can take advantage of UrlHelper
to get the URLs, as long as you do it in view:
var URL = '@Url.Action("GetDetails")';
Obviously, it doesn't make sense to put all your JavaScript in view, so what I will normal do is set just this in my view, in a namespace var, and then reference it in my external JavaScript:
View
<script>
var MyApplication = MyApplication || {};
MyApplication.GetDetailsUrl = '@Url.Action("GetDetails")';
</script>
External JS
$.get(MyApplication.GetDetailsUrl, { WONumber: wo }, function (result) {
...
});