from
function
stable
Creates an Observable from an Array, an array-like object, a Promise, an iterable object, or an Observable-like object.
from<T>(input: ObservableInput<T>, scheduler?: SchedulerLike): Observable<T>
Parameters
input |
ObservableInput<T> |
|
scheduler |
SchedulerLike |
Optional. Default is |
Returns
Description
Converts almost anything to an Observable.
from
converts various other objects and data types into Observables. It also converts a Promise, an array-like, or an iterable object into an Observable that emits the items in that promise, array, or iterable. A String, in this context, is treated as an array of characters. Observable-like objects (contains a function named with the ES2015 Symbol for Observable) can also be converted through this operator.
Examples
Converts an array to an Observable
import { from } from 'rxjs'; const array = [10, 20, 30]; const result = from(array); result.subscribe(x => console.log(x)); // Logs: // 10 // 20 // 30
Convert an infinite iterable (from a generator) to an Observable
import { from, take } from 'rxjs'; function* generateDoubles(seed) { let i = seed; while (true) { yield i; i = 2 * i; // double it } } const iterator = generateDoubles(3); const result = from(iterator).pipe(take(10)); result.subscribe(x => console.log(x)); // Logs: // 3 // 6 // 12 // 24 // 48 // 96 // 192 // 384 // 768 // 1536
With asyncScheduler
import { from, asyncScheduler } from 'rxjs'; console.log('start'); const array = [10, 20, 30]; const result = from(array, asyncScheduler); result.subscribe(x => console.log(x)); console.log('end'); // Logs: // 'start' // 'end' // 10 // 20 // 30
See Also
© 2015–2022 Google, Inc., Netflix, Inc., Microsoft Corp. and contributors.
Code licensed under an Apache-2.0 License. Documentation licensed under CC BY 4.0.
https://rxjs.dev/api/index/function/from