reduce

signature: reduce(accumulator: function, seed: any): Observable
Reduces the values from source observable to a single value that's emitted when the source completes.
💡 Just like Array.prototype.reduce()​
💡 If you need the current accumulated value on each emission, try scan!
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Examples
Example 1: Sum a stream of numbers
( StackBlitz | jsBin | jsFiddle )
// RxJS v6+
import { of } from 'rxjs';
import { reduce } from 'rxjs/operators';
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const source = of(1, 2, 3, 4);
const example = source.pipe(reduce((acc, val) => acc + val));
//output: Sum: 10'
const subscribe = example.subscribe(val => console.log('Sum:', val));
Additional Resources
​reduce 📰 - Official docs
​Scan() vs reduce() | RxJS TUTORIAL​
🎥 - Academind
​Build your own reduce operator​
🎥 - Kwinten Pisman
📁 Source Code: https://github.com/ReactiveX/rxjs/blob/master/src/internal/operators/reduce.ts​

pluck

scan

Last modified 3yr ago