web services - Structure of async callbacks in javascript: Synching the Asynch

I find the seperation of code between when using callbacks makes my code harder to understand and maintain.

How do you handle the problem?

Here are a couple of solutions I have come up with, using, as an exaple, asynch web service calls. Please let me know what you think, and and pros or cons that occur to you.

via closures:

sayHelloWithClosures: function ()
{
    //Do something first
    // The following call's signature is: ServiceName(SuccessCallback, FailureCallback);        
    TestBasicWebServices.SL.WebService1.HelloWorld(

    function (result)
    {
        //Do something next
        alert(result);
    },
    function (error)
    {
        //Do Exception
        alert(error._message);
    });

}

via recursion:

sayHello: function (result)
{
    if (result == undefined)
    {
        //Do something first

        // The following call's signature is: ServiceName(SuccessCallback, FailureCallback);
        TestBasicWebServices.SL.WebService1.HelloWorld(this.sayHello, this.sayHello);
    }
    else if (typeof (result) == "string")
    {
        //Do something next
        alert(result);
    }
    else
    {

        //Do Exception
        alert(result._message);
    }
}