Question

When doing a Ajax call to an MVC action currently I have my javascript inside the View, not inside its own JS file.

It is then very easy to do this:

var xhr = $.ajax({
     url: '<%= Url.Action("DisplayItem","Home") %>/' + el1.siblings("input:hidden").val(),
     data: { ajax: "Y" },
     cache: false,
     success: function(response) { displayMore(response, el1, xhr) }
});

…then including the URL in the ajax call using Url.Action() inside the JS is pretty easy. How could i move this do its own JS file when without hard coding the URL?

Answer 1

This way fully uses MVC Routing so you can fully take advantage of the MVC framework.
Inspired by stusmith’s answer.

Here I have an action in ApplicationController for dynamic javascript for this URL :

 /application/js

I’m including static files here because I want just one master javascript file to download. You can choose to just return the dynamic stuff if you want:

     /// <summary>
    /// Renders out javascript
    /// </summary>
    /// <returns></returns>
    [OutputCache(CacheProfile = "Script")]
    [ActionName("js")]
    public ContentResult RenderJavascript()
    {
        StringBuilder js = new StringBuilder();

        // load all my static javascript files                    
        js.AppendLine(IO.File.ReadAllText(Request.MapPath("~/Scripts/rr/cart.js")));
        js.AppendLine(";");

        // dynamic javascript for lookup tables
        js.AppendLine(GetLookupTables());
        js.AppendLine(";");

        return new ContentResult()
        {
            Content = js.ToString(),
            ContentType = "application/x-javascript"
        };
    }

This is the helper function that creates our lookup table. Just add in a line for each RouteUrl you want to use.

    [NonAction]
    private string GetLookupTables() 
    {
        StringBuilder js = new StringBuilder();

        // list of keys that correspond to route URLS
        var urls = new[] {
            new { key = "updateCart", url = Url.RouteUrl("cart-route", new { action = "updatecart" }) },
            new { key = "removeItem", url = Url.RouteUrl("cart-route", new { action = "removeitem" }) }
        };

        // lookup table function
        js.AppendLine("// URL Lookuptable");
        js.AppendLine("$.url=function(url) {");
        js.AppendLine("var lookupTable = " + new JavaScriptSerializer().Serialize(urls.ToDictionary(x=>x.key, x=>x.url)) + ";");
        js.AppendLine("return lookupTable[url];");
        js.AppendLine("}");

        return js.ToString();
    }

This generates the following dynamic javascript, which is basically just a lookup table from an arbitrary key to the URL I need for my action method :

// URL Lookuptable
$.url=function(url) {
var lookupTable = {"updateCart":"/rrmvc/store/cart/updatecart","removeItem":"/rrmvc/store/cart/removeitem"};
return lookupTable[url];
}

In cart.js I can have a function like this.
Note that the url parameter is taken from the lookup table :

 var RRStore = {};
 RRStore.updateCart = function(sku, qty) {

    $.ajax({

        type: "POST",
        url: $.url("updateCart"),
        data: "sku=" + sku + "&qty=" + qty,
        dataType: "json"

        // beforeSend: function (){},
        // success: function (){},
        // error: function (){},
        // complete: function (){},
    });

    return false;

};

I can call it from anywhere with just :

 RRStore.updateCart(1001, 5);

This seemed to be the only way I could come up with that would allow me to use routing in a clean way. Dynamically creating URLS in javascript is icky and hard to test. Testing types can add in a layer somewhere in here to easily facilitate testing.