Agapkin,
вам со скроллбаром надо или без?
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
body{
height: 2000px;
}
</style>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script>
$(function() {
alert([document.documentElement.clientWidth,window.innerWidth]);
});
</script>
</head>
<body>
</body>
</html>
