sample event emitter / observable

event-emitter.js

require('symbol-observable')
var $$observable = Symbol.observable
var rxjs = require("rxjs")
var Observable = rxjs.Observable
var Subject = rxjs.Subject

var o = new Subject()
var EventEmitter = class {
    next(item) {
        if (typeof this.observer === 'function') {
            this.observer(item)
        } else if (typeof this.observer.next === 'function') {
            this.observer.next(item)
        }
    }
    emit(item) {
        this.next(item)
    }
    subscribe(observerOrNext) {
        this.observer = observerOrNext
    }
    constructor() {
        this[$$observable] = function () {
            return this
        }
    }
}
var u = new EventEmitter();
o.takeUntil(u).subscribe(item => {
    console.log(item)
})
o.next(1)
o.next(2)
u.emit('stop')
o.next(3)