kefir/src/one-source/filter.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/one-source'

const mixin = {
  _init({fn}) {
    this._fn = fn
  },

  _free() {
    this._fn = null
  },

  _handleValue(x) {
    const fn = this._fn
    if (fn(x)) {
      this._emitValue(x)
    }
  },
}

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

const id = x => x

export default function filter(obs, fn = id) {
  return new (obs._ofSameType(S, P))(obs, {fn})
}