The Browser Object Model

The Screen

The Browser object Model provides several properties that provide information about your visitor's screen. Most of these are only of use for statistical purposes and are meaningless in so far as any JavaScript processing is concerned.

There are only two properties that are at all useful with regard to JavaScript processing and these two are only relevant with respect to those window size and position options that we discussed in the last tutorial. These are screen.availWidth and screen.availHeight which give the width and height of the available area of the screen (after subtracting any fixed toolbars) into which you can open, move, or resize a browser window.

These are the options that you should use in determining the screen size since they return the usable area of the screen where the screen.width and screen.height sizes also include any fixed toolbars which will always appear in front of the browser.

Note that nothing with regard to the screen is of any use when it comes to the JavaScript that is interacting with the browser window itself since the browser may or may not be maximised within the available area of the screen and even if it is maximised then the browser itself still takes up space on the screen leaving a smaller area to actually display your web page in. We'll look at how to actually find out the size of the browser viewport in a later tutorial.