javascript - Detect fullscreen mode

Question

Modern desktop version of IE 10 is always fullscreen.

There is a living specification for :fullscreen pseudo-class on W3

But when I tried to detect fullscreen with jQuery version 1.9.x and 2.x:

$(document).is(":fullscreen") 

it threw this error:

Syntax error, unrecognized expression: fullscreen

Questions:

1. Is it because jQuery doesn't recognize this standard yet or IE10?

2. What is the legacy way of checking fullscreen mode? I am expecting following results:

   function IsFullScreen() {
        /* Retrun TRUE */
        /* If UA exists in classic desktop and not in full screen  */
        /* Else return FALSE */
   }
   

3. Can we do it without browser sniffing?

Answer 1

As you have discovered, browser compatibility is a big drawback. After all, this is something very new.

However, since you're working in JavaScript, you have far more options available to you than if you were just using CSS.

For example:

if( window.innerHeight == screen.height) {
    // browser is fullscreen
}

You can also check for some slightly more loose comparisons:

if( (screen.availHeight || screen.height-30) <= window.innerHeight) {
    // browser is almost certainly fullscreen
}