One of the most fundamental aspects of building modern applications is user authentication. Supabase makes this incredibly straightforward with its client libraries. Whether you're using JavaScript, Python, or any other supported language, you'll find a unified API to handle user sign-up, sign-in, sign-out, and password management. This allows you to quickly implement secure user flows without reinventing the wheel.
Let's explore how you can authenticate users using the Supabase JavaScript client library. We'll cover the most common scenarios.
Before you can authenticate, you need to initialize the Supabase client. Make sure you have your Supabase URL and anon public key handy. You can find these in your Supabase project settings under the 'API' section.
import { createClient } from '@supabase/supabase-js'
const supabaseUrl = 'YOUR_SUPABASE_URL'
const supabaseAnonKey = 'YOUR_SUPABASE_ANON_KEY'
export const supabase = createClient(supabaseUrl, supabaseAnonKey)Signing up a new user is as simple as calling the signUp method. This method takes an email and password, and optionally, user metadata. Supabase will handle sending a confirmation email (if configured) and creating the user record in your auth.users table.
async function signUpNewUser() {
const { data, error } = await supabase.auth.signUp({
email: 'example@email.com',
password: 'your-secure-password',
})
if (error) {
console.error('Error signing up:', error.message)
} else {
console.log('Sign up successful! Please check your email for verification.', data)
}
}For users who already have an account, the signInWithPassword method is your go-to. Similar to sign-up, it requires an email and password.
async function signInUser() {
const { data, error } = await supabase.auth.signInWithPassword({
email: 'example@email.com',
password: 'your-secure-password',
})
if (error) {
console.error('Error signing in:', error.message)
} else {
console.log('Sign in successful!', data.user)
}
}Once a user is signed in, their session information is stored. You can access the currently authenticated user's details through the auth.user() method. This is crucial for protecting your API routes and personalizing the user experience.
const currentUser = supabase.auth.getUser()
if (currentUser) {
console.log('Currently logged in user:', currentUser.data.user)
} else {
console.log('No user is logged in.')
}Signing out a user is a one-line operation. The signOut method invalidates the current user's session on both the client and the server.
async function signOutUser() {
const { error } = await supabase.auth.signOut()
if (error) {
console.error('Error signing out:', error.message)
} else {
console.log('User signed out successfully.')
}
}Supabase also provides a convenient way to listen for authentication state changes. This is incredibly useful for updating your UI in real-time when a user signs in or out, without needing to manually poll for changes.
const { data: authListener } = supabase.auth.onAuthStateChange((event, session) => {
console.log('Auth state changed:', event, session)
// Update UI based on session status
if (session) {
// User is logged in
} else {
// User is logged out
}
})
// To unsubscribe later:
// authListener.subscription.unsubscribe()This foundational knowledge of authentication with Supabase client libraries empowers you to build secure and user-friendly applications. Remember to handle errors gracefully and consider implementing features like password reset and email verification for a robust authentication system.