Observable learning snippets. Inspired and referenced from "30天精通RxJS": https://ithelp.ithome.com.tw/articles/10187005

basic.js

//=== Using Observable.create() ===//
import Rx from 'rxjs/Rx'
let observable = Rx.Observable
  .create(observer => {
    observer.next('Jerry')
    observer.next('Anna')
  })
// OR:
// let observable = Rx.Observable.of('Jerry', 'Anna')
// let observable = Rx.Observable.from(['Jerry', 'Anna']) // **any enumerables**
observable.subscribe(value => console.log(value))

//=== a standard Observer ===//
let ob2 = Rx.Observable
  .create(observer => {
    observer.next('Jerry')
    observer.next('Anna')
    observer.complete()
    observer.next('not work')
  })
let observer2 = {
  next (value) {
    console.log(value)
  },
  error (err) {
    console.log(err)
  },
  complete () {
    console.log('complete')
  }
}
ob2.subscribe(observer2)
// Expectation:
// Jerry
// Anna
// complete

//=== 

generator.js

// A simple generator which would be use to iterate a string input and extract all numbers.
function* getNumbers(words) {
	for (let word of words) {
		if (/^[0-9]+$/.test(word)) {
		    yield parseInt(word, 10);
		}
	}
}
	
const iterator = getNumbers('30 天精通 RxJS (04)');
	
iterator.next();
// { value: 3, done: false }
iterator.next();
// { value: 0, done: false }
iterator.next();
// { value: 0, done: false }
iterator.next();
// { value: 4, done: false }
iterator.next();
// { value: undefined, done: true }

iterator.js

// A simpliest iterator
let arr = [1,2,3]
let iterator = arr[Symbol.iterator]()

iterator.next()
// { value: 1, done: false }
iterator.next()
// { value: 2, done: false }
iterator.next()
// { value: 3, done: false }
iterator.next()
// { value: undefined, done: true }

producer.js

// Producer is a very naive implementation of EventEmitter without event name.
class Producer {
  constructor () {
    this.listeners = []
  }
  
  addListener (listener) {
    if (typeof listener === 'function') {
      this.listeners.push(listener)
    } else {
      throw new Error('listener 必须是 function')
    }
  }
  
  removeListener (listener) {
    this.listeners.splice(this.listeners.indexOf(listener), 1)
  }
  
  emit (message) {
    this.listeners.forEach(listener => {
      listener(message)
    })
  }
}