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Diffstat (limited to 'common/observables.js')
| -rw-r--r-- | common/observables.js | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/common/observables.js b/common/observables.js new file mode 100644 index 0000000..f1db88c --- /dev/null +++ b/common/observables.js @@ -0,0 +1,61 @@ +/** + * This file is part of Haketilo. + * + * Function: Facilitate listening to (internal, self-generated) events. + * + * Copyright (C) 2021 Wojtek Kosior + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * As additional permission under GNU GPL version 3 section 7, you + * may distribute forms of that code without the copy of the GNU + * GPL normally required by section 4, provided you include this + * license notice and, in case of non-source distribution, a URL + * through which recipients can access the Corresponding Source. + * If you modify file(s) with this exception, you may extend this + * exception to your version of the file(s), but you are not + * obligated to do so. If you do not wish to do so, delete this + * exception statement from your version. + * + * As a special exception to the GPL, any HTML file which merely + * makes function calls to this code, and for that purpose + * includes it by reference shall be deemed a separate work for + * copyright law purposes. If you modify this code, you may extend + * this exception to your version of the code, but you are not + * obligated to do so. If you do not wish to do so, delete this + * exception statement from your version. + * + * You should have received a copy of the GNU General Public License + * along with this program. If not, see <https://www.gnu.org/licenses/>. + * + * I, Wojtek Kosior, thereby promise not to sue for violation of this file's + * license. Although I request that you do not make use this code in a + * proprietary program, I am not going to enforce this in court. + */ + +#EXPORT (value=undefined) => ({value, listeners: new Set()}) AS make +#EXPORT (observable, cb) => observable.listeners.add(cb) AS subscribe +#EXPORT (observable, cb) => observable.listeners.delete(cb) AS unsubscribe + +const silent_set = (observable, value) => observable.value = value; +#EXPORT silent_set + +const broadcast = (observable, ...values) => + observable.listeners.forEach(cb => cb(...values)); +#EXPORT broadcast + +function set(observable, value) +{ + const old_value = observable.value; + silent_set(observable, value); + broadcast(observable, value, old_value); +} +#EXPORT set |