Haketilo

/**

 * part of Hachette

 * Facilitate listening to events

 *

 * Copyright (C) 2021 Wojtek Kosior

 * Redistribution terms are gathered in the `copyright' file.

 */

const make = (value=undefined) => ({value, listeners: new Set()});

const subscribe = (observable, cb) => observable.listeners.add(cb);

const unsubscribe = (observable, cb) => observable.listeners.delete(cb);

const silent_set = (observable, value) => observable.value = value;

const broadcast = (observable, ...values) =>

      observable.listeners.forEach(cb => cb(...values));

function set(observable, value)

{

    const old_value = observable.value;

    silent_set(observable, value);

    broadcast(observable, value, old_value);

}

const observables = {make, subscribe, unsubscribe, broadcast, silent_set, set};

/*

 * EXPORTS_START

 * EXPORT observables

 * EXPORTS_END

 */