After digging trough many options, the closest I've gotten to my desired format is by declaring the elements in the namespace and then extending them with the desired functions, for which I use underscore.js. The result:
mpp_ui = {
itemList : document.getElementById('mpp_itemlist')
};
_(mpp_ui.itemList).extend({
clear : function(){
while(this.length > 0){
this.remove(0);
}
}
});