Migrating from prototye to Jquery Rails, empty() functions not working

I am migrating a rails 3 application from prototype to Jquery, .empty() function is not working on a dhtmlx grid object.

Below is the part of code which is generating error.

tree = new dhtmlXTreeObject("treeboxbox_tree","100%","100%",0);
tree.filterState.empty() // Line generating error

However when i console.log the values is an proper string and has the value which it is supposed to have.

How do i make it work in Jquery?

Can anyone also direct me to guidelines are points to be covered / implemented when migrating from prototype to Jquery

Any help would be appreciated. Thanks.