work.suroh.tk/node_modules/rxjs/_esm2015/operators/mapTo.js

53 lines
1.6 KiB
JavaScript

import { Subscriber } from '../Subscriber';
/**
* Emits the given constant value on the output Observable every time the source
* Observable emits a value.
*
* <span class="informal">Like {@link map}, but it maps every source value to
* the same output value every time.</span>
*
* <img src="./img/mapTo.png" width="100%">
*
* Takes a constant `value` as argument, and emits that whenever the source
* Observable emits a value. In other words, ignores the actual source value,
* and simply uses the emission moment to know when to emit the given `value`.
*
* @example <caption>Map every click to the string 'Hi'</caption>
* var clicks = Rx.Observable.fromEvent(document, 'click');
* var greetings = clicks.mapTo('Hi');
* greetings.subscribe(x => console.log(x));
*
* @see {@link map}
*
* @param {any} value The value to map each source value to.
* @return {Observable} An Observable that emits the given `value` every time
* the source Observable emits something.
* @method mapTo
* @owner Observable
*/
export function mapTo(value) {
return (source) => source.lift(new MapToOperator(value));
}
class MapToOperator {
constructor(value) {
this.value = value;
}
call(subscriber, source) {
return source.subscribe(new MapToSubscriber(subscriber, this.value));
}
}
/**
* We need this JSDoc comment for affecting ESDoc.
* @ignore
* @extends {Ignored}
*/
class MapToSubscriber extends Subscriber {
constructor(destination, value) {
super(destination);
this.value = value;
}
_next(x) {
this.destination.next(this.value);
}
}
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