Js validates the validity of IP and subnet mask

 
function checkIP(ip) 
{ 
obj=ip; 
var exp=/^(d{1,2}|1dd|2[0-4]d|25[0-5]).(d{1,2}|1dd|2[0-4]d|25[0-5]).(d{1,2}|1dd|2[0-4]d|25[0-5]).(d{1,2}|1dd|2[0-4]d|25[0-5])$/; 
var reg = obj.match(exp); 
if(reg==null) 
{ 
return false;//illegal
} 
else 
{ 
return true; // legal  
} 
} 

function checkMask(mask) 
{ 
obj=mask; 
var exp=/^(254|252|248|240|224|192|128|0).0.0.0|255.(254|252|248|240|224|192|128|0).0.0|255.255.(254|252|248|240|224|192|128|0).0|255.255.255.(254|252|248|240|224|192|128|0)$/; 
var reg = obj.match(exp); 
if(reg==null) 
{ 
return false; //"Illegal"
} 
else 
{ 
return true; //"Legal"
} 
}