How do I validate a Bootstrap input group with custom error messages using JavaScript?
Asked on Oct 18, 2025
Answer
To validate a Bootstrap input group with custom error messages using JavaScript, you can utilize Bootstrap's form validation classes and JavaScript to dynamically display error messages. Here's a simple example to get you started.
<!-- BEGIN COPY / PASTE -->
<form id="myForm" class="needs-validation" novalidate>
<div class="input-group mb-3">
<input type="text" class="form-control" id="username" placeholder="Username" required>
<div class="invalid-feedback">
Please enter a valid username.
</div>
</div>
<button class="btn btn-primary" type="submit">Submit</button>
</form>
<script>
(function() {
'use strict';
var form = document.getElementById('myForm');
form.addEventListener('submit', function(event) {
if (!form.checkValidity()) {
event.preventDefault();
event.stopPropagation();
}
form.classList.add('was-validated');
}, false);
})();
</script>
<!-- END COPY / PASTE -->Additional Comment:
✅ Answered with Bootstrap 5 best practices.- The `novalidate` attribute on the form prevents the default browser validation, allowing custom validation.
- The `needs-validation` class is used to style the form for validation.
- The `was-validated` class is added to the form after submission to show validation feedback.
- The `invalid-feedback` div provides a custom error message when the input is invalid.
- JavaScript checks the form's validity and prevents submission if invalid, displaying the custom error message.
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