如何在Rxjs中缓冲一个简单的可观察对象？

Question

I would like to buffer an observable by some arbitrary (but simple) criterion. I've set up a simple example here:

const observable = Rx.Observable.from([1,2,3])
const filtered = observable.filter((n) => n === 3);
observable
  .buffer(filtered)
  .subscribe((n) => {
    // Why is this empty?
    console.log(n);
});

Bin here

Trying to do this with filter only produces an empty array. I am expecting an array of [1,2,3] , but that seems to be not how it works. All the documentation for buffer uses asynchronous events like timer, but this isn't what I want. I would simply like to take the last n items based on some arbitrary criterion that I decide.

Help is much appreciated!

Answer 1

Your subscription comes after the values are emitted. If you want it to work:

const observable = new Rx.Subject()
const filtered = observable.filter((n) => n === 3);
filtered
  .buffer(filtered)
  .subscribe((n) => {
   console.log(n);
});
Rx.Observable.from([1,2,3]).subscribe(observable);

Answer 2

根据olsn的评论，看来这是Rxjs 5中的错误。更改为v4可以有效解决此问题。