• Head over to the Firebase Console.
• Click on Add project and just follow the prompts to whip up a new project.

• In the Firebase Console, go to the project settings.
• Select Add App and pick the web option (</>).
• Copy the Firebase SDK configuration code that pops up.

npm install firebase

Then, get Firebase up and running in your project:

// Import the necessary Firebase modules
import { initializeApp } from 'firebase/app';
import { getAuth } from 'firebase/auth';

// Firebase configuration object
const firebaseConfig = {
  apiKey: "YOUR_API_KEY",
  authDomain: "YOUR_PROJECT_ID.firebaseapp.com",
  projectId: "YOUR_PROJECT_ID",
  storageBucket: "YOUR_PROJECT_ID.appspot.com",
  messagingSenderId: "YOUR_MESSAGING_SENDER_ID",
  appId: "YOUR_APP_ID"
};

// Initialize Firebase
const app = initializeApp(firebaseConfig);
const auth = getAuth(app);

• In the Firebase Console, head to the Authentication section.
• Click on the Sign-in method tab.
• Turn on the Email/Password sign-in provider.

Make a form to grab user email and password for registration:

<form id="register-form">
  <input type="email" id="email" placeholder="Email" required>
  <input type="password" id="password" placeholder="Password" required>
  <button type="submit">Register</button>
</form>

Add the registration logic to create a user and send a verification email:

import { createUserWithEmailAndPassword, sendEmailVerification } from 'firebase/auth';

document.getElementById('register-form').addEventListener('submit', (e) => {
  e.preventDefault();
  
  const email = e.target.email.value;
  const password = e.target.password.value;
  
  createUserWithEmailAndPassword(auth, email, password)
    .then((userCredential) => {
      // User created, now send verification email
      sendEmailVerification(userCredential.user)
        .then(() => {
          alert('Verification email sent. Please check your inbox.');
        })
        .catch((error) => {
          console.error('Error sending email verification:', error);
        });
    })
    .catch((error) => {
      console.error('Error creating user:', error);
    });
});

In your sign-in logic, make sure to check if the user's email has been verified:

import { signInWithEmailAndPassword } from 'firebase/auth';

document.getElementById('login-form').addEventListener('submit', (e) => {
  e.preventDefault();
  
  const email = e.target.email.value;
  const password = e.target.password.value;
  
  signInWithEmailAndPassword(auth, email, password)
    .then((userCredential) => {
      const user = userCredential.user;
      if (user.emailVerified) {
        alert('User logged in successfully');
        // Proceed with the login
      } else {
        alert('Please verify your email address.');
      }
    })
    .catch((error) => {
      console.error('Error signing in:', error);
    });
});

Give users a way to request a new verification email if they didn't get it:

<form id="resend-verification-form">
  <input type="email" id="resend-email" placeholder="Email" required>
  <button type="submit">Resend Verification Email</button>
</form>

document.getElementById('resend-verification-form').addEventListener('submit', (e) => {
  e.preventDefault();
  
  const email = e.target['resend-email'].value;
  auth.fetchSignInMethodsForEmail(email)
    .then((methods) => {
      if (methods.includes('password')) {
        // Assuming user is signing in with email/password
        signInWithEmailAndPassword(auth, email, 'dummy_password')
          .then((userCredential) => {
            // Signed in successfully, now send verification email
            sendEmailVerification(userCredential.user)
              .then(() => {
                alert('Verification email resent. Please check your inbox.');
              })
              .catch((error) => {
                console.error('Error resending email verification:', error);
              });
          })
          .catch((error) => {
            console.error('Error signing in for verification email resend:', error);
          });
      }
    });
});

By following these steps, email verification can be implemented effectively using Firebase Authentication.