@xesam/timer/src/Ticker.js

a simple javascript timer wrapper

const RUNNING = 'running';
const PAUSED = 'paused';
const STOPPED = 'stopped';

const NOP = (x) => x;

class Ticker {
    constructor(onTimeout = NOP) {
        this._state = STOPPED;
        this._timerFlag = -1;
        this._flyMills = 0;
        this._timeoutMills = 0;
        this._onTimeout = onTimeout;
    }

    getElapsed() {
        return Date.now();
    }

    getState() {
        return this._state;
    }

    tick(timeout) {
        this._timerFlag = setTimeout(() => {
            this._state = STOPPED;
            this._flyMills += this.getElapsed() - this._runTime;
            this._onTimeout(this._flyMills, this);
        }, timeout);
        return true;
    }

    start(timeout = 0) {
        if (this._state !== STOPPED) {
            return false;
        }
        this._timeoutMills = timeout;
        this._flyMills = 0;
        this._runTime = this.getElapsed();
        this._state = RUNNING;
        this.tick(this._timeoutMills);
        return true;
    }

    pause() {
        if (this._state !== RUNNING) {
            return false;
        }
        this._state = PAUSED;
        clearTimeout(this._timerFlag);
        this._pauseTime = this.getElapsed();
        this._flyMills += this._pauseTime - this._runTime;
        return true;
    }

    resume() {
        if (this._state !== PAUSED) {
            return false;
        }
        this._runTime = this.getElapsed();
        this._state = RUNNING;
        this.tick(this._timeoutMills - this._flyMills);
        return true;
    }

    stop() {
        if (this._state === STOPPED) {
            return false;
        }
        this._state = STOPPED;
        clearTimeout(this._timerFlag);
        this._flyMills += this.getElapsed() - this._runTime;
        return true;
    }
}

module.exports = Ticker;