How to count number of option tags using jQuery?

Question

I have a question as to how can I calculate number of options tag when I have multiple select box with same class and id?

Let's say I have three select boxes. And I want the size of select box, so that I can dynamically add new select box with the same options:

<select id="selectid" class="selectclass">
    <option>1</option>
    <option>2</option>
</select>

<select id="selectid" class="selectclass">
    <option>1</option>
   <option>2</option>
</select>

<select id="selectid" class="selectclass">
    <option>1</option>
    <option>2</option>
</select>

Answer 1

with jquery:

for a given select with an id:

$('select#selectid option').length

for all selects with a given class:

$('select.selectclass option').length

for all selects in the page:

$('select option').length

but you should give different Ids to each element in a html page

Answer 2

Tag IDs are supposed to be unique to a document. Do you plan to have all of these in the document tree at the same time?