How to count children from different lists? [jQuery]

I'm trying to count the number of child elements a certain category has.

This is the situation:

<ul id="select_cat">
  <li id="_1">Category 1 (<span>#</span>)</li>
  <li id="_2">Category 2 (<span>#</span>)</li>
</ul>

<ul id="cat_1>
  <li>Link 1</li>
  <li>Link 2</li>
  <li>Link 3</li&开发者_如何学运维gt;
</ul>

<ul id="cat_2">
  <li>Link 1</li>
  <li>Link 2</li>
</ul> 

So I want to count the number of children a category has. In this example the first cardinal sign should be 3, and the second should be 2.

How can I do this, using jQuery.

Check an example (not jQuery)

Thanks!

$('#select_cat li').each(function() {
 $('span', this).text($('#cat' + this.id).children().length);
});

Example:

$("#cat_2").children("li").length

I have a feeling the question wants to ask something more. Anyway, it's just wiring it up to some heuristic. E.g. iterate over the "select_cat" elements with each and use their ID/position/name to count the elements in a category above and then use a text on the span (isolated with find/child), etc.

My two cents: I'd make the server do it.

You can do either of this:

alert($("#cat_1").children("li").length);
alert($("#cat_1").children("li").size());

  $("#select_cat li").each(function(){
    $("span", this).html(
      $("#cat" + $(this).attr('id')).children().size();
    );
  });