Code for entering fullscreen mode using the HTML5 fullscreen API

enter-fullscreen.js

var fullscreenAvailable = false;
var btn01 = document.getElementById('btn-01');

// Test to see if
// full-screen is available
if(
  document.fullscreenEnabled || 
  document.webkitFullscreenEnabled || 
  document.mozFullScreenEnabled ||
  document.msFullscreenEnabled
){
  fullscreenAvailable = true;
}
 
// Enter full-screen mode when btn01 
// is clicked...
btn01.addEventListener('click', function(){
	
    if(fullscreenAvailable){
        launchFullscreen(document.documentElement);	
    }else{
        alert('Sorry, fullscreen not available...');	  
    }
	
}, false);
 
// Helper function to handle 
// all the cross-browser differences 
// for entering full-screen mode
function launchFullscreen(element) {
    
    if(element.requestFullscreen) {
        element.requestFullscreen();
    } else if(element.mozRequestFullScreen) {
        element.mozRequestFullScreen();
    } else if(element.webkitRequestFullscreen) {
        element.webkitRequestFullscreen();
    } else if(element.msRequestFullscreen) {
        element.msRequestFullscreen();
    }
    
}