Method to reduce an RxJs Observable to a Promise.

reduceObservableToPromise.js

const Q = require('q');

/**
 * Method to reduce observable to a promise.
 *
 * @param observable
 */
function reduceToPromise(observable) {
    return observable.reduce((acc, item) => [...acc, item], [])
        .toPromise(Q.Promise);
}