Get value from a collection_select

how can i get the values of a form that has been filled out but was not
sent to the database.
i have a collection_select formfield and i need the selected item to
fill an DIV with content specific to the selected item.

In Javascritp i´ve done it in this way:

for (i = 0; i < document.formular.zeitung.length; ++i)
if (document.formular.zeitung.options[i].selected == true){
var textinhalt = document.formular.zeitung.options[i].value;

So in textinhalt the value is stored. How can i achieve this with ruby?