Essentials

Skipping

Reducing

Concatenating

  • startWith (soon)
  • endWith (soon)
  • concat (soon)

Combining

Animated example
How it works

take

accepts 1 input stream, an amount

  • When the input stream emits its n-th value:
    • if n < amount, the value is emitted
    • if n == amount, the value is emitted and the stream immediately completes

returns a new stream of at most amount values

filter

accepts 1 input stream, a predicate function

  • When the input stream emits a value, it is given to the predicate:
    • If the predicate returns ✔ true, the value is emitted
    • Otherwise, the value is ignored

returns a new stream of filtered values

Published on Monday, 13 Nov. 2017
Revised on Monday, 8 Oct. 2018

take

❚ take returns a new stream of at most amount values:

  • When the input stream emits its n-th value:
    • if n < amount, the event can pass
    • if n == amount, the event can pass and the stream immediately completes

Stream completion

What does “the stream completes” mean? As a reminder, a stream is a sequence of events over time. And you can subscribe to a stream, using a listener. Let’s dive into the details now:

  • A stream can emit three kinds of events:
    • values
    • an × error: e
    • a ◉ complete notification
  • After an × error: e or a ◉ complete notification, nothing else is emitted by the stream.
  • A listener can receive those three kinds of events. So, it can consume the values, handle an error and act upon completion of the subscribed stream.

See also


takeWhile

Cédric Soulas

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Freelance Developer Advocate. Motion graphics with code. JavaScript and Elm. cedricsoulas.com

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