Sha256: b644143a7ff790cb90f17a20fb1e53f4f7d7c3732071547ec88c6515e19fb3d2
Contents?: true
Size: 1.76 KB
Versions: 49
Compression:
Stored size: 1.76 KB
Contents
import { Observable } from '../Observable';
import { map } from './map';
import { OperatorFunction } from '../interfaces';
/**
* Maps each source value (an object) to its specified nested property.
*
* <span class="informal">Like {@link map}, but meant only for picking one of
* the nested properties of every emitted object.</span>
*
* <img src="./img/pluck.png" width="100%">
*
* Given a list of strings describing a path to an object property, retrieves
* the value of a specified nested property from all values in the source
* Observable. If a property can't be resolved, it will return `undefined` for
* that value.
*
* @example <caption>Map every click to the tagName of the clicked target element</caption>
* var clicks = Rx.Observable.fromEvent(document, 'click');
* var tagNames = clicks.pluck('target', 'tagName');
* tagNames.subscribe(x => console.log(x));
*
* @see {@link map}
*
* @param {...string} properties The nested properties to pluck from each source
* value (an object).
* @return {Observable} A new Observable of property values from the source values.
* @method pluck
* @owner Observable
*/
export function pluck<T, R>(...properties: string[]): OperatorFunction<T, R> {
const length = properties.length;
if (length === 0) {
throw new Error('list of properties cannot be empty.');
}
return (source: Observable<T>) => map(plucker(properties, length))(source as any);
}
function plucker(props: string[], length: number): (x: string) => any {
const mapper = (x: string) => {
let currentProp = x;
for (let i = 0; i < length; i++) {
const p = currentProp[props[i]];
if (typeof p !== 'undefined') {
currentProp = p;
} else {
return undefined;
}
}
return currentProp;
};
return mapper;
}
Version data entries
49 entries across 49 versions & 4 rubygems