Hi Yesudasan,
I tried your code.It is working properly.
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
<script src="js/main.js"></script>
<script>
var c = document.getElementById('myCanvas');
drawRectangle(c);
</script>
</head>
<body>
<canvas id="myCanvas" width="1300" height="800" style="border: 1px solid black">Your browser does not support
the HTML5 canvas tag.</canvas>
</body>
</html>