JavaScript - Form Validations

Overview

Estimated time: 10–15 minutes

Form validation ensures that user input meets requirements before submission. JavaScript can validate forms on the client side.

Learning Objectives

• Validate form fields using JavaScript.
• Provide user feedback for invalid input.

Prerequisites

• JavaScript - Page Redirects & Dialogs

Form Validation Example

const form = document.getElementById('myForm');
form.addEventListener('submit', function(event) {
  if (!form.checkValidity()) {
    event.preventDefault();
    alert('Please fill out all required fields.');
  }
});

Common Pitfalls

• Always validate on the server as well for security.

Summary

Client-side validation improves UX, but never rely on it for security—always validate on the server too.