bookmark_borderfunction call in javascript

I was studying russkey.mozdev.org source code to learn how to write Firefox extension.

Found this style of function call in javascript.

var collection =   {

 hello : function() {
  document.write("Hello World!");
 },
 
 understand : function() {
  document.write("<br/>Understand!");
 },
 
 bye : function() {
  document.write("<br/>bye!");
 }
 
};


var m = new collection.hello();
var n = new collection.understand();
var o = new collection.bye();

The output will

Hello World!
Understand!
bye!

bookmark_borderCheck date in Java Script

here is my date check javascript.

function leapyearcheck(year)
{

if(year.value % 4 != 0)
{
return 0;
}

else
{
if(year.value % 100 != 0)
{
return 1; //leap year
}

else
{

   if(year.value % 400 != 0)
   {
   return 0
   }

   else
   return 1;  //leap year

}

}
}


function datecheck(day,month,year) //call this function
{
//alert(day.value);

if(!leapyearcheck(year))
{
//alert("Not Leap Year");

   if(month.value == 2)
   {
       if(day.value > 28)
       {
       alert("Check the Day and Month");
       return false;
       }

   }
}

else

{

//alert("Leap Year");
if(month.value == 2)
   {
       if(day.value > 29)
       {
       alert("Check the Day and Month");
       return false;
       }
   }

}


Thanks to HasinHyder for a tricky one..

var dt = new Date(year+"/02/29");
if (dt.getMonth()=="1")
alert (year + " is a leap year");
else
alert(year + " is not a leap year")