JS cookies

//   cookie
document.cookie = "username = chen";
//    cookie         （  UTC   GMT   ）。     ，cookie          
document.cookie = "username = chen; expires = Thu, 18 Dec 2013 12:00:00 GMT";
//     path         cookie    
document.cookie = "username = chen; expires = Thu, 18 Dec 2013 12:00:00 GMT; path=/";

var x = document.cookie;

//   cookie       cookie
document.cookie = "username = chenchen; expires = Thu, 18 Dec 2013 12:00:00 GMT; path=/";

//   cookie     。       expires           
document.cookie = "username = chen; expires = Thu, 01 Jan 1970 00:00:00 GMT";
//  ，          cookie   。

1、   cookie     
2、   cookie     
3、   cookie     

//   cookie     
function setCookie(cname,cvalue,exdays){
    var d = new Date();
    d.setTime(d.getTime()+(exdays*24*60*60*1000));
    var expires = "expires="+d.toGMTString();
    document.cookie = cname+"="+cvalue+"; "+expires;
}
//    ：
//        ，cookie      cname，cookie     cvalue，     cookie //      expires。
//       cookie  、cookie  、cookie    。


//   cookie     
function getCookie(cname){
    var name = cname + "=";
    var ca = document.cookie.split(';');
    for(var i=0; i