Exemplo ActionResult JavaScript (MVC2,3,4,5)

homecontroller.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;

namespace MvcApplication1.Controllers
{
    [HandleError]
    public class HomeController : Controller
    {
        public ActionResult Index()
        {
            ViewData["Message"] = "Welcome to ASP.NET MVC!";

            return View();
        }

        public JavaScriptResult RetornaJs()
        {
            string script = "alert('olá');";
            
            return JavaScript(script);
        }
    }
}


//index.aspx
//<%@ Page Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage" %>

//<asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server">
//    Home Page
//</asp:Content>

//<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">
//    <h2><%: ViewData["Message"] %></h2>
//    <p>
//        To learn more about ASP.NET MVC visit <a href="http://asp.net/mvc" title="ASP.NET MVC Website">http://asp.net/mvc</a>.
//    </p>
//    <script type="text/javascript" src="/Home/RetornaJS"></script>
//</asp:Content>