Clock in Javascript

I have made a clock in javascript but its a static clock. What changes I need to do in the following code so that it updates with every second.

<html>
<head>
    <title>Javascript Clock</title>
    <script type="text/javascript">
        function clk() {
            var a=new Date();   
            document.getElementById("disp").innerHTML=a.getHours() + ":" + a.getMinutes() + ":" + a.getSeconds() ;

        }
    </script>
</head>

<body>
    <input type="button" onclick="clk()" value="Display Clock" />
    <p id="disp">Clock Space</p>
</body>

</html>

Answer

You can use setInterval to run your clk() function every second:

setInterval(clk, 1000); // run clk every 1000ms

MDN on setInterval

As nnnnnn points out, the timer interval probably won’t be synchronized with the passage of an actual, real-time second, so using an interval like 100ms might not be a bad idea.