screen
The screen object represents screen information. Commonly used attributes are:
screen.width: screen width, in pixels;
screen.height: Screen height, in pixels;
screen.colorDepth: Returns the number of color digits, such as 8, 16, 24.
<html>
<head>
<script>
'use strict';
alert('Screen size = ' + screen.width + ' x ' + screen.height);
</script>
</head>
<body>
</body>
</html>rrree