alert(typeof(NaN));   
  
alert(typeof(Infinity));  
  
alert(typeof(null));   
  
alert(typeof(undefined));   
  
alert(NaN==NaN);   
  
alert(NaN!=NaN);   
  
alert(NaN>NaN);    
  
alert(null==undefined);    
  
alert(null>=undefined);    
  
alert(null<=undefined);    
  
alert(null==null);  
  
alert(null!=null);   
  
alert(null!=NaN);   
  
alert(null==NaN);  
  
alert(NaN==undefined);   
  
alert(parseInt("123abc"));  
  
alert("123abc"-0);   
  
alert(Infinity>10);   
  
alert(Infinity>"abc");   
  
alert(Infinity==NaN);  
  
alert(true==1);   
  
alert(new String("abc")=="abc");   
  
alert(new String("abc")==="abc");   
  
   
function step(a){  
  
   return function(x){  
  
      return x+a++;  
  
   }  
  
}  
  
var a = step(10);  
  
var b = step(20);  
  
alert(a(10));  
  
alert(b(20));  
  
var a="123abc";  
  
alert(typeof(a++));  
  
alert(a);