jopek / callbag-repeat

👜 Callbag operator that repeats/restarts the stream by repeating the source handshake when source finished.

callbag-repeat

Callbag operator that repeats/restarts the source stream by repeating the source handshake when source stream finished without error.

The repeat operator can be called with repeat(n) and without repeat() parameters.

Code is based on https://github.com/Andarist/callbag-retry. The difference is that the input stream error ends the stream, while input stream end triggers a repeat.

npm install callbag-repeat

parametrized

n = 0 means no repitition: input stream = output stream. n = 1 is one repitition after source ended, n = 2 are two repititions, and so on...

const repeat = require("callbag-repeat");
const { fromIter, pipe, forEach } = require("callbag-basics");

pipe(
  fromIter("Abc"),
  repeat(2),
  forEach(v => console.log(v)) // A
                               // b
                               // c
                               // A
                               // b
                               // c
                               // A
                               // b
                               // c
)

unparametrized

Omiting the parameter means infinite repeats. The stream is stopped by either the downstream consumer with a type=2 call or by the upstream producer with an error, type=2 and data!=undefined.

const repeat = require("callbag-repeat");
const { fromIter, pipe, take, forEach } = require("callbag-basics");

pipe(
  fromIter("abc"),
  repeat(),
  take(100)
  forEach(v => console.log(v)) // A
                               // b
                               // c
                               // 96 emissions later...
                               // A
)

Endless loop of a #ball element moving up and down with sine easing in 500ms intervals:

const repeat = require("callbag-repeat");
const { fromIter, pipe, take, forEach } = require("callbag-basics");
const durationProgress = require("callbag-duration-progress");
const ball = window.document.getElementById("ball");

pipe(
  durationProgress(500),
  map(t => (1 + Math.sin(Math.PI * t - Math.PI / 2)) / 2),
  map(y => y * 300),
  repeat(),
  forEach(y => ball.style.transform = `translate3d(-35px, ${y}px, 0)` )
)