RenderRoutes renders a JSON object that contains all your named routes, as long as you're using AttributeRouting

_Layout.html

<!-- In your CSHTML file -->
<script type="text/javascript">
    window.routes = @RouteTable.Routes.RenderRoutes();
</script>

RouteExtensions.cs

// RenderRoutes extension
//
// Use with AttributeRouting and JSON.NET to
// render out a JSON object that contains all your
// named routes for use in your client scripts.

public static class RouteExtensions {
        
    /// <summary>
    /// Renders a JSON object of routes
    /// </summary>
    /// <returns></returns>
    public static IHtmlString RenderRoutes(this RouteCollection routes) {
        var json = new Dictionary<string, string>();

        foreach (IAttributeRoute route in routes.OfType<IAttributeRoute>()) {
            if (!string.IsNullOrWhiteSpace(route.RouteName) && !json.ContainsKey(route.RouteName)) {
                json.Add(route.RouteName, "/" + route.Url);
            }
        }

        // Web API
        // .OfType<>() doesn't seem to work?
        foreach (var route in GlobalConfiguration.Configuration.Routes)
        {
            if (route is IAttributeRoute)
            {
                var r = route as IAttributeRoute;
                if (!string.IsNullOrWhiteSpace(r.RouteName) && !json.ContainsKey(r.RouteName))
                {
                    json.Add(r.RouteName, "/" + r.Url);
                }
            }
        }

        return MvcHtmlString.Create(JsonConvert.SerializeObject(json));
    }
}

Router.js

// Namespace
window.app = window.app || {};

// Router utility
app.Router = (function (routes, _, undefined) {
    var router = {};    

    //
    // Public
    //
    router.url = function (routeName, parameters) {
        var finalUrl = routes[routeName];

        if (!_.isString(finalUrl)) {
            return undefined;
        }

        // Parse URL
        if (parameters) {
            if (_.isObject(parameters)) {
                // Parameter map
                for (var param in parameters) {
                    finalUrl = finalUrl.replace('{' + param + '}', parameters[param]);
                }
            } else if (parameters !== undefined) {
                // Only one parameter, replace it with given value
                var rx = new RegExp('\\{[A-z0-9_]+\\}', 'gi');

                finalUrl = finalUrl.replace(rx, parameters);
            }
        }

        return finalUrl;
    };

    return router;
})(window.routes, _);

SomeFile.js

// Somewhere else in your app...
// Given:
//     
//     window.routes = {
//         product: "/products/{productId}",
//         productPhoto: "/products/{productId}/photo/{photoId}"
//     }

app.Router.url("product", 5);
    // returns /products/5

app.Router.url("productPhoto", { productId: 5, photoId: 6 }); 
    // returns /products/5/photo/6