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What does from() do in RxJS?

AngularJunior~1 min read
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from() in RxJS is a function that turns something "ordinary" into a stream (Observable).

What you can pass to from():

  1. An array
ts
from([1, 2, 3]).subscribe(x => console.log(x)); // Outputs: 1, 2, 3 (one value at a time)
  1. A promise
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from(fetch('https://api.example.com')).subscribe(response => ...); // Fires when the promise resolves
  1. A string, Map, Set, Iterable
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from('abc').subscribe(x => console.log(x)); // Outputs: a, b, c

Why you need it:

Angular often works with Observable, but you might have a plain array or a promise, from() turns them into a reactive stream.

Conclusion:

from() is a way to take "ordinary" data and start working with it reactively. It turns an array, string, or promise into an Observable. From there you can apply .pipe(), map, filter, subscribe, and everything else.

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