Applies a given project function to each value emitted by the source Observable, and emits the resulting values as an Observable.

map<T, R>(project: (value: T, index: number) => R, thisArg?: any): OperatorFunction<T, R>

Parameters

Returns

OperatorFunction<T, R>: An Observable that emits the values from the source Observable transformed by the given project function.

Description

Like Array.prototype.map(), it passes each source value through a transformation function to get corresponding output values.

Similar to the well known Array.prototype.map function, this operator applies a projection to each value and emits that projection in the output Observable.

Example

Map every click to the clientX position of that click

import { fromEvent } from 'rxjs';
import { map } from 'rxjs/operators';

const clicks = fromEvent(document, 'click');
const positions = clicks.pipe(map(ev => ev.clientX));
positions.subscribe(x => console.log(x));

See Also

• mapTo
• pluck