第一种写法

设置cookie

 /**
      * 设置cookie
      * @param name cookie的名称
      * @param value cookie的值
      * @param day cookie的过期时间
      */
     var setCookie = function (name, value, day) {
       if(day !== 0){     //当设置的时间等于0时，不设置expires属性，cookie在浏览器关闭后删除(相当于session会话)
         var expires = day * 24 * 60 * 60 * 1000;
         var date = new Date(+new Date()+expires);
         document.cookie = name + "=" + escape(value) + ";expires=" + date.toUTCString();
       }else{
         document.cookie = name + "=" + escape(value);
       }
     }
    //setCookie('name','xiaoming',0);

获取cookie

 /**
      * 获取对应名称的cookie
      * @param name cookie的名称
      * @returns {null} 不存在时，返回null
     */
     var getCookie = function (name) {
       var arr;
       var reg = new RegExp("(^| )" + name + "=([^;]*)(;|$)");
       if (arr = document.cookie.match(reg))
         return unescape(arr[2]);
       else
         return null;
     };
    //getCookie('name');

删除cookie

/**
     * 删除cookie
     * @param name cookie的名称
     */
    var delCookie = function (name) {
      setCookie(name, ' ', -1);
    };
    //delCookie('name');

第二种写法

// Setting cookies
function set_cookie ( name, value, exp_y, exp_m, exp_d, path, domain, secure )
{
    var cookie_string = name + "=" + escape ( value );

    if (exp_y) //delete_cookie(name)
    {
        var expires = new Date ( exp_y, exp_m, exp_d );
        cookie_string += "; expires=" + expires.toGMTString();
    }

    if (path) cookie_string += "; path=" + escape ( path );
    if (domain) cookie_string += "; domain=" + escape ( domain );
    if (secure) cookie_string += "; secure";

    document.cookie = cookie_string;
}

// Retrieving cookies
function get_cookie(cookie_name)
{
    var results = document.cookie.match(cookie_name + '=(.*?)(;|$)');
    if (results) return (unescape(results[1]));
    else return null;
}

// Delete cookies
function delete_cookie( cookie_name )
{
    var cookie_date = new Date ( );  // current date & time
    cookie_date.setTime ( cookie_date.getTime() - 1 );
    document.cookie = cookie_name += "=; expires=" + cookie_date.toGMTString();
}