Iterate through dropdowns

Iterate through dropdowns

Hi,
I'm trying to iterate through all the dropdown boxes on a page without much success!
What I'd like to do is store the selected value for each of the dropdowns, separated by commas in a variable when a button is clicked.
Each of the dropdown boxes 'id' begins with the string 'attrib-' which is how I'm trying to identify them.



I've managed to hide all the dropdowns with this code:
 
jQuery(document).ready(function() {
  jQuery("#myButton").click(function() {
  jQuery("[id^=attrib-]").hide();
   })
})




So I thought I could do something similar to get the selected value but I can't figure it out.
Does anyone know if or how this can be done?