how to execute three asynchronous functions one after one

Question

i apologize if it is already asked but i have searched all over the internet and nothing has worked i am working with firestore and javascript i have tried this by far & a lot of other things

var App

  function A (){

    firebase.database().ref('Info/').once('value').then(function(snapshot){
      var Ipz = (snapshot.val() && snapshot.val().Iplist) || 'Anonymous';
      console.log(Ipz)
     })

    console.log('A')
   }


   function B (){
    console.log('B')
   }


      App = Promise.resolve();

      App = App.then(A).then(B);

      App.then(() => {
      console.log("All done");
        })

my output :-

A
B
All done
JdGJtwEe8rb394BlX4IkjUfH4Wv1;JdGJtwEe8rb394BlX4IkjUfH4Wv1;

while i want this output

JdGJtwEe8rb394BlX4IkjUfH4Wv1;JdGJtwEe8rb394BlX4IkjUfH4Wv1;
A
B
All done

Possible duplicate of Chaining promises with then and catch

P.S.
– P.S.

2018-06-20 09:03:53 +00:00
Commented Jun 20, 2018 at 9:03 — P.S.
– P.S., Commented Jun 20, 2018 at 9:03

CertainPerformance · Accepted Answer · 2018-06-20 09:02:42Z

3

You need to chain the asynchronous database function with the A, B, and all done functions using .then to connect each one:

function lookup() {
  return firebase.database().ref('Info/').once('value')
    .then(function(snapshot) {
      var Ipz = (snapshot.val() && snapshot.val().Iplist) || 'Anonymous';
      console.log(Ipz)
      // if you want to pass Ipz to `A` as a parameter, then `return Ipz;` here
    });
}
function A() {
  console.log('A');
}
function B() {
  console.log('B');
}
lookup()
  .then(A)
  .then(B)
  .then(() => console.log("All done"));

answered Jun 20, 2018 at 9:02

CertainPerformance

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