How to get relative path in Javascript?

Question

In my ASP.net web project, I've written the following Javascript code in a .js file:

function getDeviceTypes() {
    var deviceTypes;
    $.ajax({
        async: false,
        type: "POST",
        url: "Controls/ModelSelectorWebMethods.aspx/getDeviceTypes",
        data: '{ }',
        contentType: "application/json;",
        dataType: "json",
        success: function(response) {
            deviceTypes = response.d;
        },
        error: function(xhr, status) {
            debugger;
            alert('Error getting device types.');
        }
    });    // end - $.ajax
    return deviceTypes;
}

It was working great until I tried to load this .js file into a page in a subdirectory.

Let's suppose that the name of my project is widget.

When I use this code in the main virtual directory, Javascript interprets Controls/ModelSelectorWebMethods.aspx/getDeviceTypes to mean https://mysite.com/widget/Controls/ModelSelectorWebMethods.aspx/getDeviceTypes and all is well. However, from the page in a subdirectory, Javascript interprets it to mean https://mysite.com/widget/subdirectory/Controls/ModelSelectorWebMethods.aspx/getDeviceTypes and it doesn't work.

How can I write my Javascript code so that the AJAX web method can be called from pages in any directory in my application?

Answer 1

As long as you don't care about asp.net virtual directories (which makes it actually impossible to figure out from script, you'll have to pass something from the server) you can look at the URL and parse it:

function baseUrl() {
   var href = window.location.href.split('/');
   return href[0]+'//'+href[2]+'/';
}

then:

...
   url: baseUrl()+"Controls/ModelSelectorWebMethods.aspx/getDeviceTypes",
...

... and now I see from your comments above that virtual directories are a problem. I usually do this.

1) In your masterpage, put code to inject a script somewhere, preferably before anything else (I add it directly to HEAD by adding controls instead of using ScriptManager) to make sure it's run before any other script. c#:

string basePath = Request.ApplicationPath;
// Annoyingly, Request.ApplicationPath is inconsistent about trailing slash
// (if not root path, then there is no trailing slash) so add one to ensure 
// consistency if needed
string myLocation = "basePath='" + basePath + basePath=="/"?"":"/" + "';";
// now emit myLocation as script however you want, ideally in head

2) Change baseUrl to include that:

function baseUrl() {
   var href = window.location.href.split('/');
   return href[0]+'//'+href[2]+basePath;
}