04-playing-with-errors

index.mjs

import { EventEmitter } from "events";

(function (number, callback) {
    const EMITTER = new EventEmitter;
    const MILLISECONDS_INTERVAL = 50;
    const TIMESTAMP_ERROR = new Error('Timestamp is divisile by 5');
    let ticks = 0;
    let elapsedTimeInMilliseconds = 0;
    let intervalID;

    function start() {
        process.nextTick(tick);
        intervalID = setInterval(itirate, MILLISECONDS_INTERVAL)
    }

    function itirate() {
        if (elapsedTimeInMilliseconds >= number) return stop();

        elapsedTimeInMilliseconds += MILLISECONDS_INTERVAL;

        Date.now() % 5 ? tick() : propagateError();
    }

    function tick() {
        EMITTER.emit('tick');
        ticks++;
    }

    function stop() {
        clearInterval(intervalID);
        return callback(null, ticks)
    }

    function propagateError() {
        callback(TIMESTAMP_ERROR);
        EMITTER.emit('error', TIMESTAMP_ERROR);
    }

    start();
    return EMITTER;
})(1000, (error, result) => {
    if (error) {
        console.error('[Callback:]', error)
    } else {
        console.log(`Number of ticks: ${result}`)
    }
})
    .on('error', (error) => console.error('[Emitter:]', error))
    .on('tick', () => console.log('Tick'))