reduce

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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 )
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// RxJS v6+
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import { of } from 'rxjs';
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import { reduce } from 'rxjs/operators';
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​
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const source = of(1, 2, 3, 4);
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const example = source.pipe(reduce((acc, val) => acc + val));
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//output: Sum: 10'
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const subscribe = example.subscribe(val => console.log('Sum:', val));
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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​

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scan

Last modified 2yr ago

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Contents

Reduces the values from source observable to a single value that's emitted when the source completes.

Examples

Additional Resources