Getting select's value with dynamic id

Getting select's value with dynamic id

Hi;

I create multiple drop downs with php and they have different ids.  For example: 
  1. <select name="product_type[1854]" id="p_type_1854"
    onchange="update_template_for_download(p_type_1854);">
    </select>

    <select name="product_type[1854]" id="p_type_1855” 
    onchange="update_template_for_download(p_type_1855);”>
    </select>

How can I get the value of selected option? I thought this does it but this alerts "[object HTMLSelectElement]":
  1. function update_template_for_download(id)
      {
        alert(id);
       }


And alert($("#" + id).val()); alerts nothing!

Thanks