server validation with AJAX non-async

//Example: Sends an id as data to the server, save some data to the server and notify the user once it's complete.
//Note that this usage - returning the result of the call into a variable - requires a synchronous (blocking) request! (async:false)
checkform = function(formData, jqForm, opt){
var chkemail = jqForm[0].wit_email.value;
valid_check = $.ajax({url: '_tools/playbook.lasso',
global: false,
type: 'POST',
data: ({what: chkemail, route: 'validate', task: 'email'}),
dataType: 'html',
async: false}).responseText;
if(valid_check == 'true')
return true;
else{
$('input[name=wit_email]').addClass('redtext');
$('label[for=wit_email], label[for=wit_editemail]').addClass('redtext');
return false;
}
}