Javascriptプレビューコード

<textarea cols="70" rows="20" id="code"></textarea>

<script type="text/javascript">

<!--
function openWindow()
{
newWindow = window.open('','newWindow','height=300,width=500,scrollbars=auto');
if (newWindow != null)
{
var windowHTML= document.getElementById('code').value;
newWindow.document.write(windowHTML);
newWindow.focus();
}
}
//-->
</script>
<br /><br />
<input value='    ' onclick="openWindow();" type="button" />