方法名(){
             var docElm = document.documentElement; 
	         if(sessionStorage.getItem('f11') == null){
	                    if (docElm.requestFullscreen) {  
	                    docElm.requestFullscreen(); 
	                    sessionStorage.setItem('f11',1) 
	                    }  
	                        //FireFox   
	                    else if (docElm.mozRequestFullScreen) {  
	                        docElm.mozRequestFullScreen(); 
	                        sessionStorage.setItem('f11',1)  
	                    }   //Chrome等   
	                    else if (docElm.webkitRequestFullScreen) {  
	                        docElm.webkitRequestFullScreen();  
	                        sessionStorage.setItem('f11',1) 
	                    } 
	         }else{
	                    if (document.exitFullscreen) {  
	                        document.exitFullscreen();  
	                        sessionStorage.removeItem('f11') 
	                    }  
	                    else if (document.mozCancelFullScreen) {  
	                        document.mozCancelFullScreen(); 
	                        sessionStorage.removeItem('f11') 
	                    }  
	                    else if (document.webkitCancelFullScreen) {  
	                        document.webkitCancelFullScreen();
	                        sessionStorage.removeItem('f11')  
	                    }  
	                    else if (document.msExitFullscreen) {  
	                        document.msExitFullscreen();  
	                        sessionStorage.removeItem('f11')
	                    }  
	         }
}