mapto.md

mapTo

signature: mapTo(value: any): Observable

Map emissions to constant value.

Examples

Example 1: Map every emission to string

( StackBlitz | jsBin | jsFiddle )

import { interval } from 'rxjs/observable/interval';
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 )

import { fromEvent } from 'rxjs/observable/fromEvent';
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
• Smart Counter

Additional Resources

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

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