Canvas Js Function not firing,giving null error

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VS2010

<!DOCTYPE html>
<html lang="en">
<head runat="server">
<title></title>
<meta http-equiv="X-UA-Compatible" content="IE=Edge"//>
<script type="text/javascript">
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
var grd = ctx.createLinearGradient(0, 0, 175, 50);
grd.addColorStop(0, "#FF0000");
grd.addColorStop(1, "#00FF00");
ctx.fillStyle = grd;
ctx.fillRect(0, 0, 175, 50);
</script>
</head>
<body>
<form id="form1" runat="server">

</form>
</body>
</html>
what else I need to do in this? I'm using 2010 where I install SP1.HTML5 intellisense is coming on page but not in JS.

Posted 17-Jan-13 19:44pm

Rajni from delhi

Updated 17-Jan-13 19:48pm

v2

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Graham Breach · Answer 1 · 2013-01-17T22:58:00

Your script is in the header where it will be run as soon as it is loaded - which is before the canvas element has been added to the document.

You need to wait until the document has loaded before trying to use getElementById(). The easiest way is to wrap your code in an onload handler:

JavaScript

window.onload = function() {
  var c = document.getElementById("myCanvas");
  ...
  ... // more code here...
}