javascript - count the number of selections in a multiple-select box

Question

I have a multiple selection list which have more than 5 options, and i want to count the number of selection of the options selected by the user.

How to do it using java script?

I tried the following but it didn't work for me:

var x = document.getElementById("preference").count;

Thanks in Advance.

Answer 1

Assume foo is the id of the select.

If you use normal javasript:

var options = document.getElementById('foo').options, count = 0;
for (var i=0; i < options.length; i++) {
  if (options[i].selected) count++;
}

If you use jQuery:

var count = $('#foo option:selected').length;