simple debounce in onoff (nodejs gpio module)

index.js

"use strict";

const Gpio = require("onoff").Gpio;

// some kind of debouncing wrapper for watch

Gpio.prototype.watchFilter = function (callback) {
    const that = this;
    
    if (!this.watchFilterData) {
        const d = this.watchFilterData = {
            oldValue: undefined,
            timer: undefined,
            listener: []
        };

        this.watch(function (err, value) {
            if (err) {
                if (d.listener.length == 0) throw err;
                d.listener.forEach(l => l.call(that, err, value));
                return;
            }

            clearTimeout(d.timer);

            d.timer = setTimeout(function () {
                if (d.oldValue === value) return;
                d.oldValue = value;
                d.listener.forEach(l => l.call(that, undefined, value));
            }, 10); // you might need to increase this timer if you experience any problems
        });
    }

    this.watchFilterData.listener.push(callback);
};

// now what the actual code looks like:

const button = new Gpio(3, "in", "both");

button.watchFilter(function (err, value) {
    if (err) throw err;
    console.log(["off", "on"][value]);
});

related: fivdi/onoff#51