Provide URL Prefix as JS function argument

I'm writing a server which isn't necessarily accessed from a browser front end or on the same domain as the server itself. Because of this, it would be necessary to provide the address of the server as an additional argument to the generated javascript functions as so:

``` javascript
var getX = function( onSuccess
, onError
, serverAddress) // The additional server address argument
{
// ...
xhr.open('GET'
, serverAddress + '/x' // Preappend the server address to the route
, true);
// ...
}
```

But I've not found an option to do so that's not generating and modifying the API by hand constantly.