How to set value to session in external js file

[soni lal]

Hi,

I have a dropdown in my jsp. on change of this drop down a external javascript method is getting called.

I have to store the selectedindex of dropdown in session.

Please find the dropdown code in js below:
'archiveTypeFilter' : function(element){
element.onchange = function(){
var val = this.options[this.selectedIndex].value;
ACSearch.disableFilters();
ACSearch.searchAJAX(val, '0', 'y', undefined, 'facet');
}
}
here archiveTypeFilter is the name of dropdown.

Please suggest me how to do that.

Please assist me.
Thanks in advance!!