Wait for multiple promises to finish

Question

I am using the SQLStorage from the Ionic platform. The remove function returns a promise. In my code I need to remove multiple values. When these are all finished I need to execute some code.

How can I wait for all of these and then execute a callback function?

Code:

removeAll() {       this.storage.remove(key1);   this.storage.remove(key2);   this.storage.remove(key3);     } 

Nesting all is a bad practise so I am looking for a decent solution :)

removeAll() {   return this.storage.remove(key1).then(() => {     this.storage.remove(key2).then(() => {       this.storage.remove(key3);             });   }); }; 

Answer 1

You can use

removeAll() {   Promise.all([     this.storage.remove(key1),     this.storage.remove(key2),     this.storage.remove(key3),   ]).then(value => doSomething()); 

See also https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Promise/all

Answer 2

You could use Observable.forkJoin from rxjs by providing an array of all the observables/promises. This needs to be done before performing the operation. It's similar to Angular 1's $q.all.

rxjs version <= 6

Observable.forkJoin([    this.storage.remove(key1),     this.storage.remove(key2),    this.storage.remove(key3) ]) .subscribe(t=> {     var firstResult = t[0];     var secondResult = t[1]; }); 

rxjs version > 6

import {forkJoin} from 'rxjs';  forkJoin([    this.storage.remove(key1),     this.storage.remove(key2),    this.storage.remove(key3) ]) .subscribe(t=> {     var firstResult = t[0];     var secondResult = t[1]; });