您应该避免做在JavaScript中这种检测，而是通过从.NET code中的价值。你总是会冒险运行到像的HTTP URL的问题：//服务器/ MyApp的/ MyApp的/动作在那里你可以不知道这是一个控制器的名称和路径应用程序。

You should avoid doing such detection in JavaScript and instead pass the value from the .NET code. You will always risk running into problems with urls like http://server/MyApp/MyApp/action where you cannot know which is the name of a controller and which the path to the application.

在您Layout.cshtml文件（或任何你需要它）添加以下code：

In your Layout.cshtml file (or wherever you need it) add the following code:

<script type="text/javascript">
    window.applicationBaseUrl = @Html.Raw(HttpUtility.JavaScriptStringEncode(Url.Content("~/"), true));
    alert(window.applicationBaseUrl + "asd.html");

    // if you need to include host and port in the url, use this:
    window.applicationBaseUrl = @Html.Raw(HttpUtility.JavaScriptStringEncode(
        new Uri(
                   new Uri(this.Context.Request.Url.GetLeftPart(UriPartial.Authority)),
                   Url.Content("~/")
               ).ToString(), true));
    alert(window.applicationBaseUrl + "asd.html");
</script>

是必须的新的URI（）一部分，这样的URL始终正确组合（不含如果每个部分开始手动检查或 /结束符号）。

The new Uri() part is needed so that the URL is always combined correctly (without manually checking if each part starts or ends with / symbol).