Implementing Form Validation with Vanilla JS (Beginner-Friendly)

Practice Exercise: Form Validation

Objective

Create a basic form with fields for name, email, and password. Implement JavaScript validation to ensure the fields are correctly filled out before submission. This a simple code-along project meant to get you started with basic form validation in JS.

Requirements

HTML Form: Create an HTML form with inputs for name, email, and password.
CSS Styling: Add basic styling to make the form look clean and user-friendly.
JavaScript Validation: Implement JavaScript to validate the form fields.

Step-by-Step Instructions

Step 1: Set Up the HTML Structure

Create a New HTML File
- Create a new file named index.html.

Add the HTML Boilerplate

Add the basic HTML boilerplate to your file:

 <!DOCTYPE html>
 <html lang="en">
 <head>
     <meta charset="UTF-8">
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>Form Validation</title>
     <link rel="stylesheet" href="styles.css">
 </head>
 <body>
     <form id="registrationForm">
         <h2>Registration Form</h2>
         <div>
             <label for="name">Name:</label>
             <input type="text" id="name" name="name">
             <span id="nameError" class="error"></span>
         </div>
         <div>
             <label for="email">Email:</label>
             <input type="email" id="email" name="email">
             <span id="emailError" class="error"></span>
         </div>
         <div>
             <label for="password">Password:</label>
             <input type="password" id="password" name="password">
             <span id="passwordError" class="error"></span>
         </div>
         <button type="submit">Register</button>
     </form>
     <script src="script.js"></script>
 </body>
 </html>

Add the Form Elements
- Ensure your form includes fields for name, email, and password, each with a corresponding error message span.

Step 2: Add Basic CSS Styling

Create a New CSS File
- Create a new file named styles.css.

Add Basic Styles

Add basic styles to make the form look clean and user-friendly:

 body {
     font-family: Arial, sans-serif;
     display: flex;
     justify-content: center;
     align-items: center;
     height: 100vh;
     background-color: #f4f4f4;
     margin: 0;
 }

 form {
     background: #fff;
     padding: 20px;
     border-radius: 8px;
     box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
     max-width: 400px;
     width: 100%;
 }

 div {
     margin-bottom: 15px;
 }

 label {
     display: block;
     margin-bottom: 5px;
 }

 input {
     width: 100%;
     padding: 8px;
     box-sizing: border-box;
 }

 .error {
     color: red;
     font-size: 12px;
 }

 button {
     background-color: #007BFF;
     color: #fff;
     padding: 10px;
     border: none;
     border-radius: 5px;
     cursor: pointer;
 }

 button:hover {
     background-color: #0056b3;
 }

Step 3: Implement JavaScript Validation

Create a New JavaScript File
- Create a new file named script.js.

Add Event Listener to Form

Add an event listener to the form to handle form submission:

 document.getElementById('registrationForm').addEventListener('submit', function(event) {
     event.preventDefault();
     validateForm();
 });

Create the Validation Function

Add a function to validate the form fields:

 function validateForm() {
     // Clear previous error messages
     document.getElementById('nameError').innerText = '';
     document.getElementById('emailError').innerText = '';
     document.getElementById('passwordError').innerText = '';

     // Get form values
     const name = document.getElementById('name').value;
     const email = document.getElementById('email').value;
     const password = document.getElementById('password').value;

     // Validation flags
     let isValid = true;

     // Validate name
     if (name.trim() === '') {
         document.getElementById('nameError').innerText = 'Name is required';
         isValid = false;
     }

     // Validate email
     if (email.trim() === '') {
         document.getElementById('emailError').innerText = 'Email is required';
         isValid = false;
     } else if (!validateEmail(email)) {
         document.getElementById('emailError').innerText = 'Email is not valid';
         isValid = false;
     }

     // Validate password
     if (password.trim() === '') {
         document.getElementById('passwordError').innerText = 'Password is required';
         isValid = false;
     } else if (password.length < 6) {
         document.getElementById('passwordError').innerText = 'Password must be at least 6 characters';
         isValid = false;
     }

     // If all fields are valid, submit the form (for demonstration, we'll just alert a message)
     if (isValid) {
         alert('Form submitted successfully!');
     }
 }

 // Email validation function
 function validateEmail(email) {
     const re = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
     return re.test(String(email).toLowerCase());
 }

Step 4: Test the Form

Open index.html in a Browser
- Open your HTML file in a web browser to test the form validation.
- Try submitting the form with different inputs to ensure the validation works as expected.

Feel free to play around with the code and express your creativity.

Happy coding!