"debounce" in gjs

The following code is licensed under the GNU Lesser General Public License v3.0 or later:

/* exported debounce */
const {GLib} = imports.gi;

 * Copyright 2020 Dafne Kiyui
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser 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
 * GNU Lesser General Public License for more details.
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.

 * Decorate a function in a debounce wrapper
 * @param {Function} func - The function to decorate
 * @param {number} wait - Duration to wait in milliseconds
 * @param {Object} options
 * @param {number} options.priority - GLib.PRIORITY_{LOW,HIGH,..etc}
 * @returns {Function} - A debounced variant of `func`
function debounce(func, wait, options = {priority: GLib.PRIORITY_DEFAULT}) {
    let sourceId;
    return function (...args) {
        const debouncedFunc = () => {
            sourceId = null;
            func.apply(this, args);

        // It is a programmer error to attempt to remove a non-existent source
        if (sourceId)
        sourceId = GLib.timeout_add(options.priority, wait, debouncedFunc);

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A typical debounce function in JS decorates a callback function in a setTimeout block, running clearTimeout and re-decorating the callback function as the decorated function is called over time. In GJS however, neither setTimeout nor clearTimeout are defined. Instead, GLib.timeout_add is the GJS equivalent of setTimeout and setInterval in JavaScript. See the setTimeout and setInterval in gjs article for more information.