SOURCE

const Observable = rxjs.Observable;
const observable = new Observable(function(observer){
    let index = 0
    let timer = setInterval(
        function(){
            observer.next(index++)
            if (index === 3){
                // observer.error('发生错误')
                observer.complete()
                clearInterval(timer)
            }
        },1000)
})
const observer = {
    next: function(value){
        console.log(value)
    },
    error:function(value){
        console.log(value)
    }
}
observable.subscribe(observer)