57 lines
1.9 KiB
JavaScript
57 lines
1.9 KiB
JavaScript
|
/** PURE_IMPORTS_START ._map PURE_IMPORTS_END */
|
||
|
|
import { map } from './map';
|
||
|
|
/**
|
||
|
|
* 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() {
|
||
|
|
var properties = [];
|
||
|
|
for (var _i = 0; _i < arguments.length; _i++) {
|
||
|
|
properties[_i - 0] = arguments[_i];
|
||
|
|
}
|
||
|
|
var length = properties.length;
|
||
|
|
if (length === 0) {
|
||
|
|
throw new Error('list of properties cannot be empty.');
|
||
|
|
}
|
||
|
|
return function (source) { return map(plucker(properties, length))(source); };
|
||
|
|
}
|
||
|
|
function plucker(props, length) {
|
||
|
|
var mapper = function (x) {
|
||
|
|
var currentProp = x;
|
||
|
|
for (var i = 0; i < length; i++) {
|
||
|
|
var p = currentProp[props[i]];
|
||
|
|
if (typeof p !== 'undefined') {
|
||
|
|
currentProp = p;
|
||
|
|
}
|
||
|
|
else {
|
||
|
|
return undefined;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
return currentProp;
|
||
|
|
};
|
||
|
|
return mapper;
|
||
|
|
}
|
||
|
|
//# sourceMappingURL=pluck.js.map
|