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es6/operator/combineLatest.js

import { combineLatest as higherOrder } from '../operators/combineLatest';
/* tslint:enable:max-line-length */
/**
 * Combines multiple Observables to create an Observable whose values are
 * calculated from the latest values of each of its input Observables.
 *
 * <span class="informal">Whenever any input Observable emits a value, it
 * computes a formula using the latest values from all the inputs, then emits
 * the output of that formula.</span>
 *
 * <img src="./img/combineLatest.png" width="100%">
 *
 * `combineLatest` combines the values from this Observable with values from
 * Observables passed as arguments. This is done by subscribing to each
 * Observable, in order, and collecting an array of each of the most recent
 * values any time any of the input Observables emits, then either taking that
 * array and passing it as arguments to an optional `project` function and
 * emitting the return value of that, or just emitting the array of recent
 * values directly if there is no `project` function.
 *
 * @example <caption>Dynamically calculate the Body-Mass Index from an Observable of weight and one for height</caption>
 * var weight = Rx.Observable.of(70, 72, 76, 79, 75);
 * var height = Rx.Observable.of(1.76, 1.77, 1.78);
 * var bmi = weight.combineLatest(height, (w, h) => w / (h * h));
 * bmi.subscribe(x => console.log('BMI is ' + x));
 *
 * // With output to console:
 * // BMI is 24.212293388429753
 * // BMI is 23.93948099205209
 * // BMI is 23.671253629592222
 *
 * @see {@link combineAll}
 * @see {@link merge}
 * @see {@link withLatestFrom}
 *
 * @param {ObservableInput} other An input Observable to combine with the source
 * Observable. More than one input Observables may be given as argument.
 * @param {function} [project] An optional function to project the values from
 * the combined latest values into a new value on the output Observable.
 * @return {Observable} An Observable of projected values from the most recent
 * values from each input Observable, or an array of the most recent values from
 * each input Observable.
 * @method combineLatest
 * @owner Observable
 */
export function combineLatest(...observables) {
    return higherOrder(...observables)(this);
}
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