A javascript clock [Vanilla JS]

A simple javascript clock

by jjperezaguinaga

HTML

<div> <em id="hours">00</em>:<em id="minutes">00</em>:<em id="seconds">00</em>

    <br/>
    <button id="pause">Pause</button>
    <button id="resume">Resume</button>
    <button id="reset">Reset</button>
</div>

JavaScript

var Clock = {
    seconds: 23,
    minutes: 59,
    hours: 23,
    displayNumber: function (n, type) {
        this[type] = n;
        var formattedNumber = (n).toString().length == 1 ? "0" + n : n;
        document.getElementById(type).innerHTML = formattedNumber;
    },
    increase: function () {
        this.seconds = parseInt(this.seconds) + 1;
        this.displayNumber((parseInt((parseInt(+this.seconds / 60) + +this.minutes) / 60) + +this.hours) % 24, "hours");
        this.displayNumber((parseInt(+this.seconds / 60) + +this.minutes) % 60, "minutes");
        this.displayNumber(this.seconds % 60, "seconds");
    },
    start: function () {
        var that = this;
        this.interval = setInterval(function () {
            that.increase();
        }, 1000)
    },
    pause: function() {
        clearInterval(this.interval); delete this.interval;
    },
    resume: function() {
        if(!this.interval) this.start();
    },
    reset: function() {
        this.seconds = 0; this.minutes = 0; this.hours = 0;
    }
}

Clock.start();

document.getElementById("pause").addEventListener("click", Clock.pause.bind(Clock));
document.getElementById("reset").addEventListener("click", Clock.reset.bind(Clock));
document.getElementById("resume").addEventListener("click", Clock.resume.bind(Clock));