Realtime JavaScript clock

index.html

<div id="time"></div>

script.js

(function () {
    function checkTime(i) {
        return (i < 10) ? "0" + i : i; // add a zero in front of numbers<10
    }

    function startTime() {
        var today = new Date(),
            h = checkTime(today.getHours()),
            m = checkTime(today.getMinutes()),
            s = checkTime(today.getSeconds());
        document.getElementById('time').innerHTML = h + ":" + m + ":" + s;
        t = setTimeout(function () { // set Refresh rate. setTimeout() calls a function or executes a code after a specified delay
            startTime()
        }, 1000); // 1000ms = 1s. refresh clock every second
    }
    startTime();
})();

demo: http://jsfiddle.net/cse_tushar/fKKSb/311/