[jQuery] OT: looking for advise on javascript OOP

[jQuery] OT: looking for advise on javascript OOP

Hello friends,
i would like to have some advise on best javascript coding practice .
For my app i first declare an object, then the properties i will use (for easier maintenance ). But i'm unsure on how best to program my UI.refresh() function:
Basically, i pass it an object which should be compared to the existing UI object and wherever a property match, overwrite the old with the new. Everytime there is a change detected, an element must be added to a queue array. Here is my code so far.
One question i have is how best to initalise a string value: with '' or with '' or 'undefined' or ... ?
var UI = new Object();
UI.section = null;
UI.sortBy = null;
UI.dsAnchor = null;
UI.item = null;
UI.menu = null;
UI.content = null;
UI.APP_URL = null;
UI.CURRENT_URL = null;
$(document).ready(function(){
 UI.refresh = function(Obj){
        var newSection = Obj.section;
        var newSortBy = Obj.sortBy;
        var newDsAnchor = Obj.dsAnchor;
        var newItem = Obj.item;
        var newMenu = Obj.menu;
        var newContent = Obj.content;
// 1. compare current and new values. Store needed changes in queueArray
        var queueArray = new Array();
       
        if (newSection != '' && newSection != undefined && newSection != null && UI.section != newSection) {
            UI.section = newSection;
            queueArray.push('section');
        }
        if (newSortBy != '' && newSortBy != undefined && newSortBy != null && UI.sortBy != newSortBy) {
            UI.sortBy = newSortBy;
            queueArray.push('sortBy');
        }
//etc , etc...
};
});<br clear="all">
Thank you for your time !
--
Alexandre