A little bit of context:

I'm using the *jQuery Validation plugin* to validate a sign-up form. I now want to implement an **ajax call to check whether the user name is available** in the system, and I want to make this ajax call only if the userName value is a valid one as per the rules set in `$(form).validate();`

I want something like:

```
$("#userName").keyup(function () {
    if ($("#userName").isValid()) {
        //make ajax called
    }
});

```

I searched the documentation but i couldn't identify the solution to my problem.