这是供您使用的一些完整代码…一定要喜欢Google AJAX API Playground :-)
编辑1： 注意：这只允许您选择5，因为我不想复制/粘贴另外10个选项:-)
<!-- copyright (c) 2009 Google inc. You are free to copy and use this sample. License can be found here: http://pre.google.com/apis/ajaxsearch/faq/#license--><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"><html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="content-type" content="text/html; charset=utf-8"/> <title>Sample Select Maximum with jQuery</title> <script src="http://www.google.com/jsapi?key=ABQIAAAA1XbMiDxx_BTCY2_FkPh06RRaGTYH6UMl8mADNa0YKuWNNa8VNxQEerTAUcfkyrr6OwBovxn7TDAH5Q"> </script> <script type="text/javascript"> google.load("jquery", "1"); $(document).ready(function() { var last_valid_selection = null; $('#testbox').change(function(event) { if ($(this).val().length > 5) { alert('You can only choose 5!'); $(this).val(last_valid_selection); } else { last_valid_selection = $(this).val(); } }); }); </script> </head> <body > <select multiple id='testbox'> <option value='1'>First Option</option> <option value='2'>Second Option</option> <option value='3'>Third Option</option> <option value='4'>Fourth Option</option> <option value='5'>Fifth Option</option> <option value='6'>Sixth Option</option> <option value='7'>Seventh Option</option> <option value='8'>Eighth Option</option> <option value='9'>Ninth Option</option> <option value='10'>Tenth Option</option> </select> </body></html>
