Cannot understand object

[azegurb]

Hi all,
I have taken from net drop down menu script
my web page is medistyle.az. It works perfectly
but when i look up code i cannot understand one thing there
below is code (js. file)

var menu=function(){
    var t=15,z=50,s=6,a;
    function dd(n){this.n=n; this.h=[]; this.c=[]}
    dd.prototype.init=function(p,c){
        a=c; var w=document.getElementById(p), s=w.getElementsByTagName('ul'), l=s.length, i=0;
        for(i;i<l;i++){
            var h=s[i].parentNode; this.h[i]=h; this.c[i]=s[i];
            h.onmouseover=new Function(this.n+'.st('+i+',true)');
            h.onmouseout=new Function(this.n+'.st('+i+')');
        }
    }
    dd.prototype.st=function(x,f){
        var c=this.c[x], h=this.h[x], p=h.getElementsByTagName('a')[0];
        clearInterval(c.t); c.style.overflow='hidden';
        if(f){
            p.className+=' '+a;
            if(!c.mh){c.style.display='block'; c.style.height=''; c.mh=c.offsetHeight; c.style.height=0}
            if(c.mh==c.offsetHeight){c.style.overflow='visible'}
            else{c.style.zIndex=z; z++; c.t=setInterval(function(){sl(c,1)},t)}
        }else{p.className=p.className.replace(a,''); c.t=setInterval(function(){sl(c,-1)},t)}
    }
    function sl(c,f){
        var h=c.offsetHeight;
        if((h<=0&&f!=1)||(h>=c.mh&&f==1)){
            if(f==1){c.style.filter=''; c.style.opacity=1; c.style.overflow='visible'}
            clearInterval(c.t); return
        }
        var d=(f==1)?Math.ceil((c.mh-h)/s):Math.ceil(h/s), o=h/c.mh;
        c.style.opacity=o; c.style.filter='alpha(opacity='+(o*100)+')';
        c.style.height=h+(d*f)+'px'
    }
    return{dd:dd}
}();

Here i dont understand what does return{dd:dd} mean. I understand dd is name of function(class) but i couldnt understand what does syntax mean (return{dd:dd})
Thanks in advance for attention !!!

[Troy III]

It will gain you a "dd" method of "menu" object, which you can invoke with:
menu.dd(*[arg]*)

[azegurb]

I know first dd is the method and what is second dd?
dd:dd
both property and value?
Thank you for attention

[Troy III]

You are correct,
the second dd is the actual dd [object] in fact. The 'first' is its name ['handle'].

[azegurb]

Thank you very much. Now i completely understood ))