Bootstrap5 form validation

We can use different validation classes to set up the validation function of the form.

.was-validated or .needs-validation add to <form> element, the input input field will have a green (valid) or red (invalid) border effect to indicate whether the form requires input.

.valid-feedback or .invalid-feedback class is used to tell the user what information is missing or what needs to be done before submitting the form.

Example

Use .was-validated class displays what the form needs to fill in beforeit is submitted:

<form action="" class="was-validated">
  <div class="form-group">
    <label for="uname">Username:</label>
    <input type="text" class="form-control" id="uname" placeholder="Enter username" name="uname" required>
    <div class="valid-feedback">Verification successful！</div>
    <div class="invalid-feedback">Please enter your username!</div>
  </div>
  <div class="form-group">
    <label for="pwd">Password:</label>
    <input type="password" class="form-control" id="pwd" placeholder="Enter password" name="pswd" required>
    <div class="valid-feedback">Verification successful!</div>
    <div class="invalid-feedback">Please enter password!</div>
  </div>
  <div class="form-group form-check">
    <label class="form-check-label">
      <input class="form-check-input" type="checkbox" name="remember" required> consent agreement
      <div class="valid-feedback">Verification successful!</div>
      <div class="invalid-feedback">Agree to the agreement before submitting.</div>
    </label>
  </div>
  <button type="submit" class="btn btn-primary">submit to</button>
</form>

Example

Use .needs-validation which validates the missing content after the form is submitted You need to add some JavaScript code here to make the codework:

<form action="" class="needs-validation" novalidate>
  <div class="form-group">
    <label for="uname">Username:</label>
    <input type="text" class="form-control" id="uname" placeholder="Enter username" name="uname" required>
    <div class="valid-feedback">Verification successful！</div>
    <div class="invalid-feedback">enter one user name！</div>
  </div>
  <div class="form-group">
    <label for="pwd">Password:</label>
    <input type="password" class="form-control" id="pwd" placeholder="Enter password" name="pswd" required>
    <div class="valid-feedback">Verification successful！</div>
    <div class="invalid-feedback">Please enter password！</div>
  </div>
  <div class="form-group form-check">
    <label class="form-check-label">
      <input class="form-check-input" type="checkbox" name="remember" required> consent agreement
      <div class="valid-feedback">Verification successful！</div>
      <div class="invalid-feedback">Agree to the agreement before submitting。</div>
    </label>
  </div>
  <button type="submit" class="btn btn-primary">submit to</button>
</form>

<script>
// If the verification fails, prohibit submitting the form
(function() {
  'use strict';
  window.addEventListener('load', function() {
    // Get form validation style
    var forms = document.getElementsByClassName('needs-validation');
    // Loop and prohibit submission
    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>