Javascript add hours to time

Question

I have this javascript code which should show the time. It works. I wan't to be able to add extra time though. Lets say that I want to add 1 hour.

        <script type="text/javascript">
        Date.prototype.addHours = function(h) {    
           this.setTime(this.getTime() + (h*60*60*1000)); 
           return this;   
        }
        // This function gets the current time and injects it into the DOM

        function updateClock() {
            // Gets the current time
            var now = new Date();

            // Get the hours, minutes and seconds from the current time
            var hours = now.getHours();
            var minutes = now.getMinutes();
            var seconds = now.getSeconds();

            // Format hours, minutes and seconds
            if (hours < 10) {
                hours = "0" + hours;
            }
            if (minutes < 10) {
                minutes = "0" + minutes;
            }
            if (seconds < 10) {
                seconds = "0" + seconds;
            }

            // Gets the element we want to inject the clock into
            var elem = document.getElementById('clock');

            // Sets the elements inner HTML value to our clock data
            elem.innerHTML = hours + ':' + minutes + ':' + seconds;
        }
    function start(){
        setInterval('updateClock()', 200);
    }
    </script>

The first function calculates the milisecons that I want to add, and the second function is the "live clock". How do I implement the first function into the second one, so I get the working result?

Answer 1

for adding hours, use setHours :

// Gets the current time
var now = new Date();

console.log("actual time:", now);

now.setHours(now.getHours() + 1)

console.log("actual time + 1 hour:", now);

For references: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/setHours

Answer 2

Check out this fiddle.

The constructor Date(milliseconds) of class Date can be used here.

Here is the snippet.

var now = new Date();
alert(now);

var milliseconds = new Date().getTime() + (1 * 60 * 60 * 1000);
var later = new Date(milliseconds);
alert(later);