如何使用bootstrap验证表单中的电子邮件

<form>
  <div class="form-group">
    <label for="email">Email address</label>
    <input type="email" class="form-control" id="email" placeholder="Enter email">
  </div>
  <button type="submit" class="btn btn-primary">Submit</button>
</form>

<input type="email" class="form-control" id="email" placeholder="Enter email" required>

<div class="invalid-feedback">
  Please provide a valid email.
</div>

<script>
  (function() {
    'use strict';
    window.addEventListener('load', function() {
      var forms = document.getElementsByClassName('needs-validation');
      var validation = Array.prototype.filter.call(forms, function(form) {
        form.addEventListener('submit', function(event) {
          if (form.checkValidity() === false) {
            event.preventDefault();
            event.stopPropagation();
          }
          form.classList.add('was-validated');
        }, false);
      });
    }, false);
  })();
</script>