kefir/src/primary/from-sub-unsub.js

Reactive Programming library for JavaScript inspired by Bacon.js and RxJS with focus on high performance and low memory usage

import stream from './stream'
import {apply} from '../utils/functions'

export default function fromSubUnsub(sub, unsub, transformer /* Function | falsey */) {
  return stream(function(emitter) {
    let handler = transformer
      ? function() {
          emitter.emit(apply(transformer, this, arguments))
        }
      : x => {
          emitter.emit(x)
        }

    sub(handler)
    return () => unsub(handler)
  }).setName('fromSubUnsub')
}