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reduce versus scan operator in RxJS (with animations!) |
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reduce vs scan |
Monday, 26 Nov. 2018 |
❚ reduce takes the same three arguments as ❚ scan:
- an input stream
- an accumulator function (e.g. prepend a
characterto astring) - an initial value called seed (e.g.
!)
As you can see, while ❚ scan returns a new stream of progressively accumulated values, ❚ reduce returns a new stream of, at most, one value. At most? If the input stream never completes, ❚ reduce will never emit any value on the output stream.
Ultimately, ❚ reduce is equivalent to ❚ scan chained with ❚ takeLast(1).
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