如何清除ajax提交后的形式

我有一个小的联系人表单。发送消息是工作，但提交后的形式与文本保持一致。我搜索并尝试了一些代码来清除它，但没有成功。

// JavaScript Document
$('#contact-form').submit(function (e) {
"use strict";
e.preventDefault();
$.ajax({
    type: "POST",
    url: "contactform.php",
    data: $(this).serialize(), //get form values
    sucess: function (data) {
        document.getElementById("contact-form").reset();
    }
}).done(function (data) {
    console.log(data); // will contain success or invalid 
});
});

和一些php

<?php
$firstname = $_POST["firstname"];
$lastname = $_POST["lastname"];
$email = $_POST["email"];
$phone = $_POST["phone"];
$message = $_POST["message"];
$EmailTo = "marcin@rmonline.com";
$Subject = "New Message Received";
// prepare email body text
$email_content .= "Firstname: $firstname'n";
$email_content .= "Lastname: $lastname'n";
$email_content .= "Email: $email'n";
$email_content .= "Phone: $phone'n";
$email_content .= "Message: $message";
// send email
$success = mail($EmailTo, $Subject, $email_content, "From:".$email);
// redirect to success page
if ($success){
    echo "success";
} else {
    echo "invalid";
} 
?>

和

<form id="contact-form" method="post" action="contactform.php" role="form">
  <div class="messages"></div>
  <div class="form-group">
    <input id="form_name" type="text" name="firstname" class="form-control" placeholder="Please enter your firstname *" required="required" data-error="Firstname is required.">
    <div class="help-block with-errors"></div>
  </div>
  <div class="form-group">
    <input id="form_lastname" type="text" name="lastname" class="form-control" placeholder="Please enter your lastname *" required="required" data-error="Lastname is required.">
    <div class="help-block with-errors"></div>
  </div>
  <div class="form-group">
    <input id="form_email" type="email" name="email" class="form-control" placeholder="Please enter your email *" required="required" data-error="Valid email is required.">
    <div class="help-block with-errors"></div>
  </div>
  <div class="form-group">
    <input id="form_phone" type="tel" name="phone" class="form-control" placeholder="Please enter your phone">
    <div class="help-block with-errors"></div>
  </div>
  <div class="form-group">
    <textarea id="form_message" name="message" class="form-control" placeholder="Message for us *" rows="4" required data-error="Please,leave us a message."></textarea>
    <div class="help-block with-errors"></div>
  </div>
  <button type="submit" class="btn" value="Send message">Send Message</button>
  <p class="text-muted"><strong>*</strong> These fields are required.</p>
</form>

我总觉得我错过了什么，但又不知道是什么。