Email/password login in Firebase - Step-by-Step Execution

Process Flow - Email/password login

User enters email & password

↓

Send credentials to Firebase Auth

↓

Firebase checks credentials

↓

Valid?

↓

User logged in

↓

Access granted to app

User inputs email and password, Firebase verifies them, then either logs the user in or shows an error.

Execution Sample

Firebase

firebase.auth().signInWithEmailAndPassword(email, password)
  .then(userCredential => {
    // User logged in
  })
  .catch(error => {
    // Show error
  });

This code tries to log in a user with email and password using Firebase Authentication.

Process Table

Step	Action	Input	Firebase Response	Result
1	User inputs email and password	email: [e-mail], password: secret123	N/A	Credentials ready to send
2	Send credentials to Firebase	email & password	Checking credentials	Waiting for response
3	Firebase validates credentials	email & password	Valid user found	Success
4	Return user info	N/A	User logged in	Access granted
5	App receives user info	User object	N/A	User session started

💡 Login successful, user session started

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
email	undefined	[e-mail]	[e-mail]	[e-mail]	[e-mail]	[e-mail]
password	undefined	secret123	secret123	secret123	secret123	secret123
userCredential	undefined	undefined	undefined	{user info}	{user info}	{user info}
error	undefined	undefined	undefined	undefined	undefined	undefined

Key Moments - 3 Insights

Why does the app wait after sending credentials?

Because Firebase needs time to check the email and password against its database before responding, as shown in step 2 and 3 of the execution table.

What happens if the email or password is wrong?

Firebase returns an error instead of user info, so the catch block runs to show an error message. This is not shown here because the example shows a successful login.

Why do we need the userCredential variable?

It holds the logged-in user's information returned by Firebase, which the app uses to start the user session, as seen in steps 4 and 5.

Visual Quiz - 3 Questions

Look at the execution table, what is the Firebase response at step 3?

A Valid user found

B Waiting for response

C User logged in

D Error message shown

💡 Hint

Check the 'Firebase Response' column in row 3 of the execution table.

At which step does the app receive the user object?

A Step 4

B Step 3

C Step 5

D Step 2

💡 Hint

Look at the 'Result' column to see when the user session starts.

If the password was incorrect, which variable would change in the variable tracker?

A email

B error

C userCredential

D password

💡 Hint

Errors are stored in the 'error' variable when login fails.

Concept Snapshot

Email/password login with Firebase:
- User inputs email and password
- Call signInWithEmailAndPassword(email, password)
- Firebase checks credentials
- On success, returns user info
- On failure, returns error
- Use .then() for success, .catch() for errors

Full Transcript

This visual execution shows how email and password login works with Firebase Authentication. The user enters their email and password. These credentials are sent to Firebase, which checks if they match a registered user. If valid, Firebase returns user information and the app starts a user session. If invalid, Firebase returns an error and the app shows a message. Variables like email, password, userCredential, and error track the process. The execution table details each step from input to login success.