IE下不能disabled掉select标签的option的解决方案

今天在工作中需要用到disabled掉一些select的option，结果发现IE6没有实现它。
还好我们下载select-option-disabled-emulation.js文件即可自动完成disabled标记的工作，代码也很少:

/****************************************************************
* Author:   Alistair Lattimore
* Website:  http://www.lattimore.id.au/
* Contact:  http://www.lattimore.id.au/contact/
*           Errors, suggestions or comments
* Date:     30 June 2005
* Version:  1.0
* Purpose:  Emulate the disabled attributte for the <option>
*           element in Internet Explorer.
* Use:      You are free to use this script in non-commercial
*           applications. You are however required to leave
*           this comment at the top of this file.
*
*           I'd love an email if you find a use for it on your
*           site, though not required.
****************************************************************/

window.onload = function() {
     if (document.getElementsByTagName) {
         var s = document.getElementsByTagName("select");

         if (s.length > 0) {
             window.select_current = new Array();

             for (var i=0, select; select = s[i]; i++) {
                 select.onfocus = function(){ window.select_current[this.id] = this.selectedIndex; }
                 select.onchange = function(){ restore(this); }
                emulate(select);
            }
        }
    }
}

function restore(e) {
     if (e.options[e.selectedIndex].disabled) {
        e.selectedIndex = window.select_current[e.id];
    }
}

function emulate(e) {
     for (var i=0, option; option = e.options[i]; i++) {
         if (option.disabled) {
             option.style.color = "graytext";
        }
         else {
             option.style.color = "menutext";
        }
    }
}