combineLatest.js
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"use strict";
var isScheduler_1 = require('../util/isScheduler');
var isArray_1 = require('../util/isArray');
var ArrayObservable_1 = require('./ArrayObservable');
var combineLatest_1 = require('../operator/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 all the 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 = Rx.Observable.combineLatest(weight, 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 {Observable} observable1 An input Observable to combine with the
* source Observable.
* @param {Observable} observable2 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.
* @param {Scheduler} [scheduler=null] The Scheduler to use for subscribing to
* each input 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.
* @static true
* @name combineLatest
* @owner Observable
*/
function combineLatest() {
var observables = [];
for (var _i = 0; _i < arguments.length; _i++) {
observables[_i - 0] = arguments[_i];
}
var project = null;
var scheduler = null;
if (isScheduler_1.isScheduler(observables[observables.length - 1])) {
scheduler = observables.pop();
}
if (typeof observables[observables.length - 1] === 'function') {
project = observables.pop();
}
// if the first and only other argument besides the resultSelector is an array
// assume it's been called with `combineLatest([obs1, obs2, obs3], project)`
if (observables.length === 1 && isArray_1.isArray(observables[0])) {
observables = observables[0];
}
return new ArrayObservable_1.ArrayObservable(observables, scheduler).lift(new combineLatest_1.CombineLatestOperator(project));
}
exports.combineLatest = combineLatest;
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