How do you make a promise with firebase .on() function?-CodePudding

I am trying to use Firebase .on() method in order to check whenever a new account has been made in my realtime Firebase database. Now since I am encrypting this data in the Firebase Database, I would like to the first time the data from the firebase is loaded to decrypt it using a function that I made. Is it possible I could make something like a promise that will allow me to do this once the firebase loaded all the data in my variable?

var users2 = database.ref("users/").on("value", (snapshot) => {
      const usersLst = snapshot.val();
      users = usersLst
});

I would like to add something like this:

var users2 = database.ref("users/").on("value", (snapshot) => {
      const usersLst = snapshot.val();
      users = usersLst
}).then(() => {
      console.log(decryptAccounts(users))
});

One important thing that I want to keep is the .on() function since that will allow me to constantly check whether someone has created a new account in the database. Does anyone have any ideas what is another approach I could use to achieve the same thing?

CodePudding user response：

You can just add the decryptAccounts() functions inside on() so everytime an update is received, you can run that function on that data.

var users2 = database.ref("users/").on("value", (snapshot) => {
      const usersLst = snapshot.val();
      
      // runs on new value fetched after every update
      decryptAccounts(usersLst)
})

CodePudding user response：

You can store the ref in a variable to reuse it like the docs suggest.

const databaseRef = database.ref("users/");
// use databaseRef.get() with the correct path to your attribute you want to get
// Runs only once
databaseRef.get().then((snapshot) => {
  // Decrypt function
});
// Listens to changes
var users2 = databaseRef .on("value", (snapshot) => {
      const usersLst = snapshot.val();
      users = usersLst
});

This first gets the values once and then you can decrypt them, when the values change the .on function will be fired again.

CodePudding user response：

The answer that I found with the help of Dharmaraj was that you can just do this:

database.ref("users/").on("value", (snapshot) => {
    decryptAccounts(snapshot.val());
});

This would get the values from the database every time and decrypt them.