Source Code: (back to article)
<form id="myForm">
Enter your name: <input type="text" name="username" required>
<input type="submit" value="Submit">
</form>
<div id="formFeedback"></div>

<script>
document.getElementById('myForm').addEventListener('submit', function(event) {
var input = this.username.value;
if (input.length < 4) {
event.preventDefault(); // Prevent form from submitting
document.getElementById('formFeedback').textContent = 'Name must be at least 4 characters long.';
} else {
document.getElementById('formFeedback').textContent = 'Form submitted successfully!';
}
});
</script>