kefir/src/two-sources/filter-by.js

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

import {createStream, createProperty} from '../patterns/two-sources'
import {NOTHING} from '../constants'

const mixin = {
  _handlePrimaryValue(x) {
    if (this._lastSecondary !== NOTHING && this._lastSecondary) {
      this._emitValue(x)
    }
  },

  _handleSecondaryEnd() {
    if (this._lastSecondary === NOTHING || !this._lastSecondary) {
      this._emitEnd()
    }
  },
}

const S = createStream('filterBy', mixin)
const P = createProperty('filterBy', mixin)

export default function filterBy(primary, secondary) {
  return new (primary._ofSameType(S, P))(primary, secondary)
}