How to update/insert an other document in cloud firestore on receiving a create event for a collection using functions

Question

Let us assume that we have two collections say "users" and "usersList"

Upon creating a new user document in users collection with following object

{username: Suren, age:31}

The function should read the above data and update other collection i.e. "usersList" with the username alone like below

{username: Suren}

Let me know the possibility

The code I have tried is

exports.userCreated = 
functions.firestore.document('users/{userId}').onCreate((event) => {
   const post = event.data.data();

   return event.data.ref.set(post, {merge: true});
})

Answer 1

I have done it using below code

exports.userCreated = functions.firestore.document('users/{userId}')
.onCreate((event) => {
    const firestore = admin.firestore()
    return firestore.collection('usersList').doc('yourDocID').update({
        name:'username',
      }).then(() => {
        // Document updated successfully.
        console.log("Doc updated successfully");
      });
})