$(document).on("click",".dialog button", function(e){
(e).preventDefault();

var name    = $("input[name='name']").val();
var email   = $("input[name='email']").val();
var message = $("textarea[name='message']").val();

var emailReg = /^[a-zA-Z0-9._+-]+@[a-zA-Z0-9-]+\.[a-zA-Z]{2,4}(\.[a-zA-Z]{2,3})?(\.[a-zA-Z]{2,3})?$/;

var nameIsValid = name.length >= 1,
    emailIsValid = emailReg.test(email),
    messageIsValid = message.length >= 1;

error = !(nameIsValid && emailIsValid && messageIsValid);

// client-side validation
if(!nameIsValid) 
    $("input[name='name']").addClass("error");
else
    $("input[name='name']").removeClass("error");

if(!emailIsValid)
    $("input[name='email']").addClass("error");
else
    $("input[name='email']").removeClass("error");

if(!messageIsValid) 
    $("textarea[name='message']").addClass("error");
else
    $("textarea[name='message']").removeClass("error");

if (error == false) {

    $.ajax({
        type: "post",
        dataType: "json",
        url: "lib/email.php",
        data: $("#contactform").serialize(),
        success: function(data) { }
    });

    };

});