How To Write Javascript Code For Login Page

How To Articles

Writing JavaScript code for a login page can seem a bit intimidating at first, but with a little bit of knowledge and practice, you’ll be able to create a secure and user-friendly login experience for your website. In this article, I’ll guide you through the process of writing JavaScript code for a login page, sharing personal tips and insights along the way.

Understanding the Login Process

Before we dive into writing JavaScript code, it’s important to understand the login process and the key components involved. A typical login page consists of an input field for the username or email, another input field for the password, and a login button to submit the form.

When a user enters their credentials and clicks the login button, our JavaScript code will be responsible for handling the authentication process. This involves validating the input fields, checking if the credentials match the ones stored in the database, and redirecting the user to their dashboard or displaying an error message if the login fails.

Creating the HTML Structure

First, let’s create the HTML structure for our login page. We’ll need an HTML form element to wrap our input fields and login button. Each input field should have a unique ID so that we can easily target them with JavaScript.


<form id="login-form">
  <input type="text" id="username" placeholder="Username or Email">
  <input type="password" id="password" placeholder="Password">
  <button id="login-btn">Login</button>
</form>

Adding Event Listeners

Now that we have our HTML structure in place, we can start writing our JavaScript code. We’ll start by adding event listeners to the login button, which will trigger the login process when clicked.


const loginForm = document.getElementById('login-form');
const loginButton = document.getElementById('login-btn');

loginButton.addEventListener('click', function(event) {
  event.preventDefault();
  const username = document.getElementById('username').value;
  const password = document.getElementById('password').value;

  // Perform authentication and redirection logic here
});

In the code above, we first grab references to the login form and login button using their respective IDs. Then, we attach an event listener to the login button’s click event. Inside the event listener, we prevent the default form submission behavior, retrieve the values of the username and password fields, and perform any necessary authentication logic.

Implementing Authentication Logic

Now comes the most crucial part – implementing the authentication logic. Depending on your website’s requirements, you might need to send an HTTP request to a server-side endpoint for authentication. For simplicity, let’s assume we have a predefined list of valid credentials stored in an array.


const validCredentials = [
  { username: 'john_doe', password: 'password123' },
  { username: 'jane_smith', password: 'qwerty9876' }
];

function performLogin(username, password) {
  for (let i = 0; i < validCredentials.length; i++) {
    if (validCredentials[i].username === username && validCredentials[i].password === password) {
      return true;
    }
  }

  return false;
}

loginButton.addEventListener('click', function(event) {
  event.preventDefault();
  const username = document.getElementById('username').value;
  const password = document.getElementById('password').value;

  if (performLogin(username, password)) {
    window.location.href = 'dashboard.html'; // Redirect to dashboard
  } else {
    alert('Invalid username or password');
  }
});

In the code above, we define a function performLogin which accepts the username and password as parameters. Inside the function, we loop through the validCredentials array and check if any of the entries match the provided username and password. If a match is found, we return true, indicating successful authentication. Otherwise, we return false.

Back in the event listener for the login button, we call the performLogin function with the entered username and password. If the function returns true, we redirect the user to the dashboard.html page using the window.location.href property. If the function returns false, we display an alert with an error message.

Conclusion

Writing JavaScript code for a login page may seem daunting at first, but with a solid understanding of the login process and some practice, you’ll be able to create a secure and user-friendly login experience for your website.

We covered the basics of creating the HTML structure, adding event listeners, and implementing the authentication logic. Remember to always follow best practices for handling user credentials to ensure the security of your website.

Now that you have the foundation, feel free to customize and enhance your login page with additional features such as password hashing, password strength validation, and remember me functionality. Happy coding!