@reactivex/rxjs
Version:
Reactive Extensions for modern JavaScript
65 lines • 2.06 kB
JavaScript
;
Object.defineProperty(exports, "__esModule", { value: true });
var map_1 = require("./map");
/* tslint:enable:max-line-length */
/**
* 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>
*
* 
*
* 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
* Map every click to the tagName of the clicked target element
* ```ts
* import { fromEvent } from 'rxjs';
* import { pluck } from 'rxjs/operators';
*
* const clicks = fromEvent(document, 'click');
* const tagNames = clicks.pipe(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
*/
function pluck() {
var properties = [];
for (var _i = 0; _i < arguments.length; _i++) {
properties[_i] = arguments[_i];
}
var length = properties.length;
if (length === 0) {
throw new Error('list of properties cannot be empty.');
}
return function (source) { return map_1.map(plucker(properties, length))(source); };
}
exports.pluck = pluck;
function plucker(props, length) {
var mapper = function (x) {
var currentProp = x;
for (var i = 0; i < length; i++) {
var p = currentProp != null ? currentProp[props[i]] : undefined;
if (p !== void 0) {
currentProp = p;
}
else {
return undefined;
}
}
return currentProp;
};
return mapper;
}
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