Is it possible to set limit in multiple selection dropdown list?

问题

I am using a multiple selection drop-down list in my site.This is working properly and we can select more than one options from that list.But I want select only 3 options from that list.Is it possible to set limit for that??

I am using the code from http://www.aleixcortadellas.com/main/2009/03/20/492/

回答1:

use jQuery and following click function, it will help

$(document).ready(function() 
{
    $('#slectboxid option').click(function() 
    {
        var items = $(this).parent().val();
        if (items.length > 3) {
                       alert("You can only select 3 values at a time");
           $(this).removeAttr("selected");
        }
    });
   });

Edit: use .prop() instead of .removeAttr(),.removeAttr() is deprecated in newest jQuery libraries

回答2:

In formsubmit.php change line 3 with the following line :

if (isset($options) && count($options) == 3) {

Then modify line 26 with the following :

echo 'Please select exactly 3 options';

来源：https://stackoverflow.com/questions/10410169/is-it-possible-to-set-limit-in-multiple-selection-dropdown-list