13.5.11 - concatAll、concatMap

concatAll：有时 Observable 发出的又是一个 Obervable，concatAll 的作用就是将新的可观察对象和数据源进行合并

import { fromEvent, interval } from "rxjs"
import { map, take, concatAll } from "rxjs/operators"
fromEvent(document, "click")
  .pipe(
    map(event => interval(1000).pipe(take(2))),
    concatAll()
  )
.subscribe(console.log)

import { map, concatAll } from "rxjs/operators"
import { of, interval } from "rxjs"
interval(1000)
  .pipe(
    map(val => of(val + 10)),
    concatAll()
  )
.subscribe(console.log)

concatMap：合并可观察对象并处理其发出的数据流