User profile data in Firebase - Step-by-Step Execution

Process Flow - User profile data

User signs up or logs in

↓

Check if profile exists in Firestore

↓

Load profile

↓

User views or edits profile

↓

Save changes to Firestore

↓

Profile updated

This flow shows how user profile data is checked, created if missing, loaded, edited, and saved in Firebase Firestore.

Execution Sample

Firebase

const userId = auth.currentUser.uid;
const profileRef = firestore.collection('profiles').doc(userId);
const doc = await profileRef.get();
if (!doc.exists) {
  await profileRef.set({name: '', email: ''});
}

This code checks if a user profile exists in Firestore; if not, it creates a new empty profile.

Process Table

Step	Action	Condition	Result	Firestore State
1	Get current user ID	N/A	userId = 'abc123'	No change
2	Reference profile document	N/A	profileRef points to 'profiles/abc123'	No change
3	Get profile document	N/A	doc fetched	No change
4	Check if doc exists	doc.exists == false	Profile does not exist	No change
5	Create new profile	N/A	Set {name:'', email:''} in Firestore	New profile created at 'profiles/abc123'
6	End	N/A	Profile ready for use	Profile document exists

💡 Profile created because it did not exist before

Status Tracker

Variable	Start	After Step 1	After Step 3	After Step 5	Final
userId	undefined	'abc123'	'abc123'	'abc123'	'abc123'
doc.exists	undefined	undefined	false	false	false
profileRef	undefined	undefined	ref to 'profiles/abc123'	ref to 'profiles/abc123'	ref to 'profiles/abc123'

Key Moments - 2 Insights

Why do we check if the profile document exists before creating it?

Because creating a profile without checking could overwrite existing data. See execution_table step 4 where doc.exists is false, so we create the profile only then.

What happens if the profile already exists?

The code skips creating a new profile and uses the existing data. This is implied by the condition in step 4; if doc.exists was true, creation would be skipped.

Visual Quiz - 3 Questions

Look at the execution_table at step 4, what is the value of doc.exists?

A true

B undefined

C false

D null

💡 Hint

Check the 'Condition' column in step 4 of execution_table

At which step is the new profile created in Firestore?

A Step 3

B Step 5

C Step 4

D Step 6

💡 Hint

Look at the 'Action' and 'Result' columns in execution_table

If the profile document already existed, which step would be skipped?

A Step 5

B Step 3

C Step 2

D Step 6

💡 Hint

Refer to the condition in step 4 and what happens next in execution_table

Concept Snapshot

User profile data in Firebase Firestore:
- Check if profile document exists using get()
- If not exists, create with set()
- Use user ID as document key
- Load and update profile data as needed
- Always check existence to avoid overwriting

Full Transcript

This visual execution shows how Firebase Firestore handles user profile data. First, the app gets the current user's ID. Then it references the profile document in the 'profiles' collection using that ID. It fetches the document to check if it exists. If the profile does not exist, the app creates a new profile document with empty fields. This prevents overwriting existing profiles. Finally, the profile is ready for use or editing. Variables like userId and doc.exists change as the code runs. Key moments include why existence is checked and what happens if the profile exists. The quiz tests understanding of these steps.