var res = checkOS(); 
if(res == true){ 
	alert("WIN"); 
}else if(res == false){ 
	alert("MAC"); 
}else{ 
	alert("ERROR"); 
} 
 
/* 
 * a function to check the operating system 
 *  
 * @returns true if the OS is windows 
 */ 
 
function checkOS(){ 
	var os_string = $.os; 
	var os_char = os_string.charAt(0); 
	var bool = null; 
	if (os_char == "w" || os_char == "W") { 
		bool = true; 
	} 
	else { 
		bool = false; 
	} 
return bool; 
} 

var str_os = ($.os.search(/windows/i) != -1) ? 'Win' : 'Mac' 

var str_os = ($.os.search(/macintosh/i) != -1) ? 'Mac' : 'Win' 

 
var res = checkOS();  
if((res[0] == true)&&(res[1]== false)){  
	alert("This is windows");  
}else if((res[0] == false)&&(res[1]== true)){  
	alert("This is macintosh");  
}else{  
	alert("ERROR");  
}  
  
/*  
 * a function to check the operating system  
 *   
 * @returns array of boolean 
 */  
  
function checkOS(){  
    var os_w = null; 
    var os_m = null; 
    os_w = ($.os.search(/windows/i) != -1) ? true : false; 
    os_m = ($.os.search(/macintosh/i) != -1) ? true : false; 
    return [os_w,os_m]; 
 
} 

if (File.fs == "Macintosh") { 
	alert("Das ist wohl ein Mac"); 
} else if (File.fs == "Windows") { 
	alert("Ach was, Windows..."); 
} else { 
	alert("Huch! Unix?"); 
}