mapto.md

mapTo

signature: mapTo(value: any): Observable

Map emissions to constant value.

{% hint style="info" %}

New to transformation operators? Check out the article Get started transforming streams with map, pluck, and mapTo!

{% endhint %}

Examples

Example 1: Map every emission to string

( StackBlitz | jsBin | jsFiddle )

// RxJS v6+
import { interval } from 'rxjs';
import { mapTo } from 'rxjs/operators';

//emit value every two seconds
const source = interval(2000);
//map all emissions to one value
const example = source.pipe(mapTo('HELLO WORLD!'));
//output: 'HELLO WORLD!'...'HELLO WORLD!'...'HELLO WORLD!'...
const subscribe = example.subscribe(val => console.log(val));

Example 2: Mapping clicks to string

( StackBlitz | jsBin | jsFiddle )

// RxJS v6+
import { fromEvent } from 'rxjs';
import { mapTo } from 'rxjs/operators';

//emit every click on document
const source = fromEvent(document, 'click');
//map all emissions to one value
const example = source.pipe(mapTo('GOODBYE WORLD!'));
//output: (click)'GOODBYE WORLD!'...
const subscribe = example.subscribe(val => console.log(val));

Related Recipes

• HTTP Polling
• Save Indicator
• Smart Counter
• Stop Watch

Additional Resources

• mapTo 📰 - Official docs
• Changing behavior with mapTo 🎥 💵 - John Linquist
• Transformation operator: map and mapTo 🎥 💵 - André Staltz

---

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