reactive-programmingxstream-js

Emit a stream only if value changed

Using xstream, how can I create a stream that only emits when it's input stream emits a new value

Here is a diagram

input  -----1--1-1--2-3--3--3---5-|
output -----1-------2-3---------5-|
Solution

  • While the core xstream library is comprised of a few well chosen operators, additional operators are included as extras and can accessed by their path.

    import xs from 'xstream';
import dropRepeats from 'xstream/extra/dropRepeats'

const stream = xs.of(1, 1, 1, 2, 3, 3, 3, 5)
  .compose(dropRepeats())

stream.addListener({
   next: i => console.log(i),
   error: err => console.error(err),
   complete: () => console.log('completed')
});

    The .compose operator is used to drop the extra methods into the stream.

    source: https://github.com/staltz/xstream/blob/master/EXTRA_DOCS.md#dropRepeats