Counting the number of option tags in a select tag in jQuery

Question

$('#input1 option').length;

This will produce 2.

The W3C solution:

var len = document.getElementById("input1").length;

You can use either length property and length is better on performance than size.

$('#input1 option').length;

OR you can use size function like (removed in jQuery v3)

$('#input1 option').size(); 

$(document).ready(function(){
   console.log($('#input1 option').size());
   console.log($('#input1 option').length);
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<select data-attr="dropdown" id="input1">
   <option value="Male" id="Male">Male</option>
   <option value="Female" id="Female">Female</option>
</select>

Your question is a little confusing, but assuming you want to display the number of options in a panel:

<div id="preview"></div>

and

$(function() {
  $("#preview").text($("#input1 option").length + " items");
});

Not sure I understand the rest of your question.

In a multi-select option box, you can use $('#input1 :selected').length; to get the number of selected options. This can be useful to disable buttons if a certain minimum number of options aren't met.

function refreshButtons () {
    if ($('#input :selected').length == 0)
    {
        $('#submit').attr ('disabled', 'disabled');
    }
    else
    {
        $('#submit').removeAttr ('disabled');
    }
}

Ok, i had a few problems because i was inside a

$('.my-dropdown').live('click', function(){  
});

I had multiples inside my page that's why i used a class.

My drop down was filled automatically by a ajax request when i clicked it, so i only had the element $(this)

so...

I had to do:

$('.my-dropdown').live('click', function(){
  total_tems = $(this).find('option').length;
});