topromise.md

toPromise

signature: toPromise() : Promise

Convert observable to promise.

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⚠ toPromise is not a pipable operator, as it does not return an observable.

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Examples

Example 1: Basic Promise

( jsBin | jsFiddle )

//return basic observable
const sample = val => Rx.Observable.of(val).delay(5000);
//convert basic observable to promise
const example = sample('First Example')
  .toPromise()
  //output: 'First Example'
  .then(result => {
    console.log('From Promise:', result);
  });

Example 2: Using Promise.all

( jsBin | jsFiddle )

//return basic observable
const sample = val => Rx.Observable.of(val).delay(5000);
/*
  convert each to promise and use Promise.all
  to wait for all to resolve
*/
const example = () => {
  return Promise.all([
    sample('Promise 1').toPromise(),
    sample('Promise 2').toPromise()
  ]);
};
//output: ["Promise 1", "Promise 2"]
example().then(val => {
  console.log('Promise.all Result:', val);
});

Additional Resources

• toPromise 📰 - Official Docs

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📁 Source Code: https://github.com/ReactiveX/rxjs/blob/master/src/internal/operators/toPromise.ts