On ModX Login Add-On : How do I add AJAX/JQuery capabilities with this Add-On

								<fieldset id="signin_menu">
<div class="loginMessage" id="msg">[[+errors]]</div>
<div id="contact_form">  
	<form class="loginLoginForm" method="post" name="contact" id="signin" action="">
										<p>									
											<label for="username">[[%login.username]]
											<input id="username" class="loginUsername" type="text" name="username" tabindex="4" />
											</label>
										</p>
										<p>
											<label for="password">[[%login.password]]
											<input id="password" class="loginPassword" type="password" name="password" tabindex="5" />
											</label>
											<input class="returnUrl" type="hidden" name="returnUrl" value="[[+request_uri]]" />
										</p>
										<p class="remember">
											<input type="button" id="login" value="[[+actionMsg]]" />
											<input id="remember" name="remember_me" value="1" tabindex="7" type="checkbox">
											<label for="remember">Remember me</label>
											[[+login.recaptcha_html]]			

											<input class="loginLoginValue" type="hidden" name="service" value="login" />
											
										</p>
										<p class="forgot-username"> 
											<a id=forgot_username_link title="If you remember your password, try logging in with your email" href="[[~12]]">Forgot your username?</a><br>
											<a id=forgot_username_link title="Apply for Membership" href="[[~15]]">Apply for Membership</a><br>											
										</p>
									</form>
</div>									
								</fieldset>

   $("#username").keyup(function(e){
		if(e.keyCode == 13){
                        var value = $("#username").val();
                        var datastr = "p_text="+value;
			$.ajax({
			type:'POST',
			url:'[[~22]]',
			data: $('signin'),
			success:function(data){
				$("#msg").html(data);
			}
		   });
		}
	});

require_once $modx->getOption('login.core_path',null,$modx->getOption('core_path').'components/login/').'model/login/login.class.php';
$login = new Login($modx,$scriptProperties);
if (!is_object($login) || !($login instanceof Login)) return '';

$controller = $login->loadController('Login');
$output = $controller->run($scriptProperties);
return $output;