kefir/src/interop/from-promise.js

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

import stream from '../primary/stream'
import toProperty from '../one-source/to-property'

export default function fromPromise(promise) {
  let called = false

  let result = stream(function(emitter) {
    if (!called) {
      let onValue = function(x) {
        emitter.emit(x)
        emitter.end()
      }
      let onError = function(x) {
        emitter.error(x)
        emitter.end()
      }
      let _promise = promise.then(onValue, onError)

      // prevent libraries like 'Q' or 'when' from swallowing exceptions
      if (_promise && typeof _promise.done === 'function') {
        _promise.done()
      }

      called = true
    }
  })

  return toProperty(result, null).setName('fromPromise')
}