Is There A Way To Detect The Width Of The Browser Scrolling Bar?

Is there a way to detect with javascript the scrolling bar with of the
browser?

My problem is that the the following script assing to the pos variable the browser window size but only internet explorer substracts the scrolling bar with from the result.

<script language="JavaScript" type="text/JavaScript">
<!--
var pos;
if (window.innerWidth)
{
pos =window.innerWidth;
}
else if (document.documentElement &&
document.documentElement.clientWidth)
{
pos= document.documentElement.clientWidth;
}
else if (document.body)
{
pos= document.body.clientWidth;
}
//-->
</script>

At least i want to ask if there is a script that return exactly the width of the browser's window that i have to output any text or graphic?