kefir/src/one-source/last.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'
import {NOTHING} from '../constants'

const mixin = {
  _init() {
    this._lastValue = NOTHING
  },

  _free() {
    this._lastValue = null
  },

  _handleValue(x) {
    this._lastValue = x
  },

  _handleEnd() {
    if (this._lastValue !== NOTHING) {
      this._emitValue(this._lastValue)
    }
    this._emitEnd()
  },
}

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

export default function last(obs) {
  return new (obs._ofSameType(S, P))(obs)
}