var services={
    title:"Services",
    dropdown:["Buy","Sell","GTFO"]
};
var contacts={
    title:"Contacts",
    dropdown:["1","2","3","4"]

};
var aboutUs={
    title:"About us",
    dropdown:["3","4"]
};
var menu=[services, contacts, aboutUs];

var ul = document.createElement("ul");
document.body.appendChild(ul);

for(i in menu){
    var li = document.createElement("li");
    ul.appendChild(li);
    li.innerHTML=menu[i].title;

    if(menu[i].dropdown != null && menu[i].dropdown.length!=0){
        var ul2 = document.createElement("ul");
        li.appendChild(ul2);
        ul2.style.display="none";


        for(j in menu[i].dropdown){
            var li2 = document.createElement("li");
            ul2.appendChild(li2);
            li2.innerHTML = menu[i].dropdown[j];
        };
    }
};
li.onmouseover=function(){
    ul2.style.display="block";
     }