jquery通过扩展select控件实现支持enter或focus选择的方法

/***************************************
* @ author jdkleo
* @ date 2013/2/27
 JQuery SelKeys
USAGE:
 jQuery.selkeys.enter(jQuery("#selcon"));
 jQuery.selkeys.focus(jQuery("#selcon2"));
*****************************************/
(function (jQuery){
 this.version = '(beta)(0.0.1)';
 this.all = {};
 /**---------enter---------**/
 this.enter = function(sel){ 
  var flag = 1;
  var open = function(){ 
   if(flag==1){
    sel.get(0).size = sel.get(0).options.length;
    flag=0;
   }else{
    sel.get(0).size = 1;
    flag=1;
   }
  }; 
  sel.keydown(function(e){ 
    e = e ? e :(window.event ? window.event : null); 
    var code = e.keyCode || e.which || e.charCode;
    if(code == 13)
    {
     open();
     return false;
    }
   });
  sel.blur(function(){
     sel.get(0).size=1;
     flag=1;
     });   
 } 
 /**---------focus---------**/
 this.focus = function(sel){ 
  var flag = 1;
  var open = function(){ 
   if(flag==1){
    sel.get(0).size = sel.get(0).options.length;
    flag=0;
   }else{
    sel.get(0).size = 1;
    flag=1;
   }
  }; 
  sel.focus(function(){ 
    open();
    return false;
   });
  sel.blur(function(){
    sel.get(0).size=1;
    flag=1;
   });
  sel.keydown(function(e){ 
    e = e ? e :(window.event ? window.event : null); 
    var code = e.keyCode || e.which || e.charCode;
    if(code == 13)
    {
     sel.get(0).size=1;
     flag=1;
     return false;
    }
   });
 }
 /**---------all---------**/
 jQuery.selkeys = this;
 return jQuery; 
})(jQuery);