publish

为了方便，RxJS 提供了 publishXXX operator 作为 multicast 的简写：

publish:         multicast + Subject
publishReplay:   multicast + ReplaySubject
publishBehavior: multicast + BehaviorSubject
publishAsync:    multicast + AsyncSubject

看个例子：

const shared = Rx.Observable.interval(1000)
  .do(x => console.log(`source ${x}`))
  .publishReplay(100)
  .refCount();

const observerA = {
  next: x => console.log(`A next ${x}`),
  error: e => console.error(`A error ${e}`),
  complete: () => console.log('A done')
};

// refCount: 0 --> 1 开始
const subA = shared.subscribe(observerA);

const observerB = {
  next: x => console.log(`B next ${x}`),
  error: e => console.error(`B error ${e}`),
  complete: () => console.log('B done')
};

let subB;
setTimeout(() => {
  // refCount: 1 --> 2
  subB = shared.subscribe(observerB);
}, 2000);

setTimeout(() => {
  // refCount: 2 --> 1
  subA.unsubscribe();
  console.log('unsubscribe A');
}, 5000);

setTimeout(() => {
  // refCount: 1 --> 0 停止
  subB.unsubscribe();
  console.log('unsubscribe B');
}, 7000);

/* 程序输出：
  "source 0"
  "A next 0"
  "source 1"
  ...
  "source 4"
  "A next 4"
  "B next 4"
  "unsubscribe A"
  "source 5"
  "B next 5"
  "source 6"
  "B next 6"
  "unsubscribe B"
*/

查看例子