handling contact form error animation – HTML/CSS/JS

//Contact Form Redirection
var form = document.getElementById("my-form");

async function handleSubmit(event) {
  event.preventDefault();
  var data = new FormData(event.target);
  fetch(event.target.action, {
    method: form.method,
    body: data,
    headers: {
      'Accept': 'application/json'
    }
  }).finally(() => {
    window.location = "thankyou.html";
  });
}
myform.firstname.oninvalid = badEntrie
myform.lastname.oninvalid = badEntrie
myform.email.oninvalid = badEntrie
myform.subject.oninvalid = badEntrie

function badEntrie({
  target
}) {
  target.classList.add('shakingErr')
  setTimeout(() => {
    target.classList.remove('shakingErr')
  }, 820)
}
form.addEventListener("submit", handleSubmit)

//Contact Form Error Animation 
document.querySelector('form').addEventListener('submit', function(e) {
  var isValid = true;
  this.querySelectorAll('input, textarea').forEach(function(f) {
    if (!f.checkValidity()) {
      isValid = false;
      f.style.borderColor = "red";
      f.style.animation = "shake 0.82s forwards";
      setTimeout(function() {
        f.style.animation = "unset";
      }, 820);
    } else {
      f.style.borderColor = "initial";
    }
  })
  if (!isValid) {
    e.preventDefault();
  }
})

/* Contact Form */

input[type=text],
[type=email],
select,
textarea {
  width: 100%;
  padding: 12px;
  border: 1px solid #555;
  margin-top: 6px;
  margin-bottom: 16px;
  resize: vertical;
}

input[type=submit] {
  background-color: #0563bb;
  color: white;
  padding: 12px 20px;
  border: none;
  cursor: pointer;
}

input[type=submit]:hover {
  opacity: 0.9;
}

.contactform {
  position: relative;
  border-radius: 50px;
  background-color: #f2f2f2;
  padding: 5px;
  z-index: 2;
  display: block;
  margin-left: auto;
  margin-right: auto;
  margin-bottom: auto;
  margin-top: 1%;
  width: 100%;
  animation-name: gradient;
  animation-duration: 3s;
  animation-iteration-count: infinite;
}

.contactform:hover {
  animation-name: gradient;
  animation-duration: 15s;
  animation-iteration-count: infinite;
}

.column {
  float: center;
  width: 50%;
  margin-top: 6px;
  padding: 20px;
  display: block;
  margin-left: auto;
  margin-right: auto;
}

.row:after {
  content: "";
  display: table;
  clear: both;
}

@media screen and (max-width: 600px) {
  .column,
  input[type=submit] {
    width: auto;
    margin-top: 0;
  }
}

.shakingErr {
  border-color: red;
  animation: shake 0.82s forwards;
}

@keyframes shake {
  10%,
  90% {
    transform: translate3d(-1px, 0, 0);
  }
  20%,
  80% {
    transform: translate3d(2px, 0, 0);
  }
  30%,
  50%,
  70% {
    transform: translate3d(-4px, 0, 0);
  }
  40%,
  60% {
    transform: translate3d(4px, 0, 0);
  }
}

<section id="contact">
  <div class="container" data-aos="fade-up">
    <div class="contactform">
      <div style="text-align:center">
        <div class="section-title">
          <h2><br/>Get In Touch</h2>
        </div>
        <p>Feel Free To Reach Out To Me Through This Form! </p>
      </div>
      <div class="row">
        <div class="column">
          <form name="myform" action="https://formspree.io/f/xdobkgny" id="my-form" method="POST">
            <label for="firstname">First Name</label>
            <input type="text" id="first name" name="firstname" placeholder="Your First Name.." required>
            <label for="lastname">Last Name</label>
            <input type="text" id="lastname" name="lastname" placeholder="Your Last Name.." required>
            <label for="email">Email:</label>
            <input type="email" id="email" name="email" placeholder="Your Email.." required>
            <label for="subject">Subject</label>
            <textarea id="subject" name="subject" placeholder="Lets Collaborate.." style="height:170px" required></textarea>
            <input type="submit" value="Submit">
          </form>
        </div>
      </div>
    </div>
  </div>
</section>