code: function toggleFullScreen(elm) {
  
      if ((document.fullScreenElement && 
           document.fullScreenElement !== null) ||    
          (!document.mozFullScreen && !document.webkitIsFullScreen)) {
          if (elm.requestFullScreen) {  
              elm.requestFullScreen();  
          } else if (elm.mozRequestFullScreen) {  
              elm.mozRequestFullScreen();  
          } else if (elm.webkitRequestFullScreen) {  
            elm.webkitRequestFullScreen();  
        }  
      } else {  
          if (document.cancelFullScreen) {  
            document.cancelFullScreen();  
          } else if (document.mozCancelFullScreen) {  
            document.mozCancelFullScreen();  
          } else if (document.webkitCancelFullScreen) {  
            document.webkitCancelFullScreen();  
          }  
      }  
  }
docs: show full screen mode, like F11 toggleFullScreen();