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

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2019-12-02 12:22:45 +00:00
import { Subscriber } from '../Subscriber';
/**
* Applies a given `project` function to each value emitted by the source
* Observable, and emits the resulting values as an Observable.
*
* <span class="informal">Like [Array.prototype.map()](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map),
* it passes each source value through a transformation function to get
* corresponding output values.</span>
*
* <img src="./img/map.png" width="100%">
*
* 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 <caption>Map every click to the clientX position of that click</caption>
* var clicks = Rx.Observable.fromEvent(document, 'click');
* var positions = clicks.map(ev => ev.clientX);
* positions.subscribe(x => console.log(x));
*
* @see {@link mapTo}
* @see {@link pluck}
*
* @param {function(value: T, index: number): R} project The function to apply
* to each `value` emitted by the source Observable. The `index` parameter is
* the number `i` for the i-th emission that has happened since the
* subscription, starting from the number `0`.
* @param {any} [thisArg] An optional argument to define what `this` is in the
* `project` function.
* @return {Observable<R>} An Observable that emits the values from the source
* Observable transformed by the given `project` function.
* @method map
* @owner Observable
*/
export function map(project, thisArg) {
return function mapOperation(source) {
if (typeof project !== 'function') {
throw new TypeError('argument is not a function. Are you looking for `mapTo()`?');
}
return source.lift(new MapOperator(project, thisArg));
};
}
export class MapOperator {
constructor(project, thisArg) {
this.project = project;
this.thisArg = thisArg;
}
call(subscriber, source) {
return source.subscribe(new MapSubscriber(subscriber, this.project, this.thisArg));
}
}
/**
* We need this JSDoc comment for affecting ESDoc.
* @ignore
* @extends {Ignored}
*/
class MapSubscriber extends Subscriber {
constructor(destination, project, thisArg) {
super(destination);
this.project = project;
this.count = 0;
this.thisArg = thisArg || this;
}
// NOTE: This looks unoptimized, but it's actually purposefully NOT
// using try/catch optimizations.
_next(value) {
let result;
try {
result = this.project.call(this.thisArg, value, this.count++);
}
catch (err) {
this.destination.error(err);
return;
}
this.destination.next(result);
}
}
//# sourceMappingURL=map.js.map