adapt username availibility check code - passwords

Question

I need your help to adapt a code that displays if a username is already taken.
This code is working :
$(document).ready(function()
{
$("#name").keyup(function()
{
var name = $(this).val();
$.post( "username-check.php", { name: $("#name").val() }, function (data){
if(data=='1'){
//the php post result is equal to '1' if the username is already taken.
// This actualy display "1" in the form if the username is taken.
$("#result").html(data);
}
}); //function(data)
});
})
I got this code from a website, to check and validate the inputs of my form
$('document').ready(function()
{
// Check and validate the username input
var nameregex = /^[a-zA-Z0-9 ]+$/;
$.validator.addMethod("validname", function( value, element ) {
return this.optional( element ) || nameregex.test( value );
});
/* To check if the username is taken I think I have to add something like that :
var checkusernameregex = ??????;
$.validator.addMethod("checkusername", function( value, element ) {
return this.optional( element ) || checkusernameregex.test( value );
}); */
$("#register-form").validate({
rules:
{
name: {
required: true,
validname: true,
//chekusername : true,
minlength: 5,
maxlength: 25
}
},
messages:
{
name: {
required: "Please choose a username",
validname: "Username can only have alphanumerical characters ",
//checkusername: "Username already taken";
minlength: "Username is too short"
}
},
});
//to display errors code, but not needed for my actual request
Thank you