RocketChat/Rocket.Chat

import { Tracker } from 'meteor/tracker';

export const waitUntilFind = <T>(fn: () => T | undefined): Promise<T> =>
    new Promise((resolve) => {
        Tracker.autorun((c) => {
            const result = fn();

            if (result === undefined) {
                return;
            }

            c.stop();
            resolve(result);
        });
    });