‘use strict‘const extend = require(‘xtend‘)const EventEmitter = require(‘events‘)class ObservableStore extends EventEmitter { ?constructor (initState = {}) { ???super() ???// set init state ???this._state = initState ?} ?// wrapper around internal getState ?getState () {//输出值 ???return this._getState() ?} ???// wrapper around internal putState ?putState (newState) { ???this._putState(newState)//存储newState值 ???this.emit(‘update‘, newState)//并触发subscribe中的‘update‘事件，并调用相应的handler函数 ?} ?updateState (partialState) {//更改里面的一部分的值 ???// if non-null object, merge ???if (partialState && typeof partialState === ‘object‘) { ?????const state = this.getState() ?????const newState = Object.assign({}, state, partialState) ?????this.putState(newState) ???// if not object, use new value ???} else { ?????this.putState(partialState) ???} ?} ?// subscribe to changes ?subscribe (handler) { ???this.on(‘update‘, handler) ?} ?// unsubscribe to changes ?unsubscribe (handler) { ???this.removeListener(‘update‘, handler)//移除‘update‘事件 ?} ?// ?// private ?// ?// read from persistence ?_getState () { ???return this._state ?} ?// write to persistence ?_putState (newState) { ???this._state = newState ?}}module.exports = ObservableStore

const DuplexStream = require(‘stream‘).Duplexmodule.exports = asStreamfunction asStream(obsStore) { ?return new ObsStoreStream(obsStore)}////////class ObsStoreStream extends DuplexStream { ?constructor(obsStore) { ???super({ ?????// pass values, not serializations ?????objectMode: true, ???}) ???// dont buffer outgoing updates ???this.resume() ???// save handler so we can unsubscribe later ???this.handler = (state) => this.push(state) ???// subscribe to obsStore changes ???this.obsStore = obsStore ???this.obsStore.subscribe(this.handler) ?} ?// emit current state on new destination ?pipe (dest, options) {//调用pipe函数，将obsStore.getState()值传到dest ???const result = DuplexStream.prototype.pipe.call(this, dest, options) ???dest.write(this.obsStore.getState()) ???return result ?} ?// write from incomming stream to state ?_write (chunk, encoding, callback) { ???this.obsStore.putState(chunk) ???callback() ?} ?// noop - outgoing stream is asking us if we have data we arent giving it ?_read (size) { } ?// unsubscribe from event emitter ?_destroy (err, callback) { ???this.obsStore.unsubscribe(this.handler); ???super._destroy(err, callback) ?}}

‘use strict‘const ObservableStore = require(‘../‘)class LocalStorageStore extends ObservableStore { ?constructor (opts = {}) { ???if (!global.localStorage) throw new Error(‘LocalStorageStore - can\‘t find localStorage.‘)//global.localStorage即浏览器本身是否有本地存储 ???super() ???this._storageKey = opts.storageKey ???if (!this._storageKey) throw new Error(‘LocalStorageStore - no storageKey specified.‘) ?} ?// ?// private ?// ?// read from persistence ?_getState () { ???const serialized = global.localStorage.getItem(this._storageKey)//不同的_storageKey对应的是本地存储的不同内容 ???return serialized ? JSON.parse(serialized) : undefined ?} ?// write to persistence ?_putState (newState) { ???const serialized = JSON.stringify(newState) ???return global.localStorage.setItem(this._storageKey, serialized) ?}}module.exports = LocalStorageStore

‘use strict‘const test = require(‘tape‘)const pipe = streamUtils.pipeconst ObservableStore = require(‘../‘)const asStream = require(‘../lib/asStream‘)const TEST_WAIT = 200test(‘basic stream‘, function(t){ ?t.plan(2) ?const initState = ‘init‘ ?const nextState = ‘next‘ ?const storeOne = new ObservableStore(initState)//在初始化时就存储值initState ?const storeTwo = new ObservableStore()//在初始化时并没有存储值 ?storeTwo.once(‘update‘, (value) => {//监听一次‘update‘事件 ???initValueCheck(value)//查看value值与initState值是否相同 ???storeTwo.once(‘update‘, nextValueCheck)//再监听一次查看与nextState的值是否相同 ?}) ?pipe(//将storeOne流中的值initState传给storeTwo流，storeTwo调用putState时会调用一次‘update‘事件，查看是否于initState值相同 ???asStream(storeOne), ???asStream(storeTwo) ?) ?storeOne.putState(nextState)//将storeOne中的值从initState改变成nextState，这里又会触发一次‘update‘事件，这次是查看是否于nextState相同 ?function initValueCheck(value){ ???t.equal(value, initState, ‘storeTwo subscribed: state is initState‘) ?} ?function nextValueCheck(value){ ???t.equal(value, nextState, ‘storeTwo subscribed: state is nextState‘) ?}})test(‘double stream‘, function(t){ ?t.plan(4) ?const initState = ‘init‘ ?const nextState = ‘next‘ ?const storeOne = new ObservableStore(initState) ?const storeTwo = new ObservableStore() ?storeTwo.once(‘update‘, (initValue) => { ???initValueCheck(‘storeTwo‘, initValue) ???storeTwo.once(‘update‘, (nextValue) => nextValueCheck(‘storeTwo‘, nextValue)) ?}) ?const storeThree = new ObservableStore() ?storeThree.once(‘update‘, (initValue) => { ???initValueCheck(‘storeThree‘, initValue) ???storeThree.once(‘update‘, (nextValue) => nextValueCheck(‘storeThree‘, nextValue)) ?}) ?pipe( ???asStream(storeOne), ???asStream(storeTwo)//storeTwo触发一次‘update‘ ?) ?pipe( ???asStream(storeOne), ???asStream(storeThree)//storeThree触发一次‘update‘ ?) ?storeOne.putState(nextState)//将会导致storeTwo、storeThree再分别触发一次 ?function initValueCheck(label, value){ ???t.equal(value, initState, `${label} subscribed: state is initState`) ?} ?function nextValueCheck(label, value){ ???t.equal(value, nextState, `${label} subscribed: state is nextState`) ?}})

‘use strict‘const test = require(‘tape‘)const LocalStorageStore = require(‘../lib/localStorage‘)test(‘localStorage - localStorage presence validation‘, function(t){ ?t.plan(2) ?t.notOk(global.localStorage, ‘global.localStorage not defined‘) ?t.throws(() => { ???new LocalStorageStore({ storageKey: ‘test‘ }) ?}, Error, ‘throws error when localStorage is not defined‘)})test(‘localStorage - storageKey validation‘, function(t){ ?t.plan(2) ?global.localStorage = createLocalStorage() ?t.ok(global.localStorage, ‘global.localStorage is defined‘) ?t.throws(() => { ???new LocalStorageStore() ?}, Error, ‘throws error when opts.storageKey is not defined‘)})test(‘localStorage - basic test‘, function(t){ ?t.plan(2) ?global.localStorage = createLocalStorage() ?t.ok(global.localStorage, ‘global.localStorage is defined‘) ?const store = new LocalStorageStore({ storageKey: ‘test‘ }) ?store.putState(42) ?t.equal(store.getState(), 42, ‘store works roundtrips values great‘)})test(‘localStorage - obj test‘, function(t){ ?t.plan(2) ?global.localStorage = createLocalStorage() ?t.ok(global.localStorage, ‘global.localStorage is defined‘) ?const store = new LocalStorageStore({ storageKey: ‘test‘ }) ?store.putState({ a: 123 }) ?t.deepEqual(store.getState(), { a: 123 }, ‘store works roundtrips obj values great‘)})function createLocalStorage() { ?const values = {} ?const localStorage = {} ?localStorage.getItem = (key) => values[key] ?localStorage.setItem = (key, value) => values[key] = value ?return localStorage}