> For the complete documentation index, see [llms.txt](https://chasethestar.gitbook.io/ko.learn-rxjs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://chasethestar.gitbook.io/ko.learn-rxjs/rxjs/operators/combination/concatall.md).

# concatAll

#### signature: `concatAll(): Observable`

## Collect observables and subscribe to next when previous completes.

***

⚠ Be wary of [backpressure](https://github.com/Reactive-Extensions/RxJS/blob/master/doc/gettingstarted/backpressure.md) when the source emits at a faster pace than inner observables complete!

💡 In many cases you can use [concatMap](/ko.learn-rxjs/rxjs/operators/transformation/concatmap.md) as a single operator instead!

***

[![Ultimate RxJS](https://drive.google.com/uc?export=view\&id=1qq2-q-eVe-F_-d0eSvTyqaGRjpfLDdJz)](https://ultimatecourses.com/courses/rxjs?ref=4)

### Examples

( [example tests](https://github.com/btroncone/learn-rxjs/blob/master/operators/specs/combination/concatall-spec.ts) )

**Example 1: concatAll with observable**

( [StackBlitz](https://stackblitz.com/edit/typescript-zwtpc7?file=index.ts\&devtoolsheight=100) | [jsBin](http://jsbin.com/nakinenuva/1/edit?js,console) | [jsFiddle](https://jsfiddle.net/btroncone/8dfuf2y6/) )

```js
// RxJS v6+
import { map, concatAll } from 'rxjs/operators';
import { of, interval } from 'rxjs';

//emit a value every 2 seconds
const source = interval(2000);
const example = source.pipe(
  //for demonstration, add 10 to and return as observable
  map(val => of(val + 10)),
  //merge values from inner observable
  concatAll()
);
//output: 'Example with Basic Observable 10', 'Example with Basic Observable 11'...
const subscribe = example.subscribe(val =>
  console.log('Example with Basic Observable:', val)
);
```

**Example 2: concatAll with promise**

( [StackBlitz](https://stackblitz.com/edit/typescript-3w4px3?file=index.ts\&devtoolsheight=100) | [jsBin](http://jsbin.com/bekegeyopu/1/edit?js,console) | [jsFiddle](https://jsfiddle.net/btroncone/w7kp7qLs/) )

```js
// RxJS v6+
import { map, concatAll } from 'rxjs/operators';
import { interval } from 'rxjs';

//create and resolve basic promise
const samplePromise = val => new Promise(resolve => resolve(val));
//emit a value every 2 seconds
const source = interval(2000);

const example = source.pipe(
  map(val => samplePromise(val)),
  //merge values from resolved promise
  concatAll()
);
//output: 'Example with Promise 0', 'Example with Promise 1'...
const subscribe = example.subscribe(val =>
  console.log('Example with Promise:', val)
);
```

**Example 3: Delay while inner observables complete**

( [StackBlitz](https://stackblitz.com/edit/typescript-ft3rbf?file=index.ts\&devtoolsheight=100) | [jsBin](http://jsbin.com/pojolatile/1/edit?js,console) | [jsFiddle](https://jsfiddle.net/btroncone/8230ucbg/) )

```js
// RxJS v6+
import { take, concatAll } from 'rxjs/operators';
import { interval, of } from 'rxjs';

const obs1 = interval(1000).pipe(take(5));
const obs2 = interval(500).pipe(take(2));
const obs3 = interval(2000).pipe(take(1));
//emit three observables
const source = of(obs1, obs2, obs3);
//subscribe to each inner observable in order when previous completes
const example = source.pipe(concatAll());
/*
  output: 0,1,2,3,4,0,1,0
  How it works...
  Subscribes to each inner observable and emit values, when complete subscribe to next
  obs1: 0,1,2,3,4 (complete)
  obs2: 0,1 (complete)
  obs3: 0 (complete)
*/

const subscribe = example.subscribe(val => console.log(val));
```

### Related Recipes

* [Progress Bar](/ko.learn-rxjs/rxjs/recipes/progressbar.md)

### Additional Resources

* [concatAll](https://rxjs.dev/api/operators/concatAll) 📰 - Official docs
* [concatAll](https://indepth.dev/reference/rxjs/operators/concat-all) - In Depth Dev Reference
* [Flatten a higher order observable with concatAll in RxJS](https://egghead.io/lessons/rxjs-flatten-a-higher-order-observable-with-concatall-in-rxjs?course=use-higher-order-observables-in-rxjs-effectively) 🎥 💵 - André Staltz

***

> 📁 Source Code: <https://github.com/ReactiveX/rxjs/blob/master/src/internal/operators/concatAll.ts>


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://chasethestar.gitbook.io/ko.learn-rxjs/rxjs/operators/combination/concatall.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.