cookie指某些网站为了辨别用户身份、进行session跟踪而储存在用户本地终端上的数据（通常经过加密）
在网站客户端中保存数据，可以减少服务器的压力

// Cookie操作对象
var Cookies = {};
// cookie设置
Cookies.set = function(name, value){
     var argv = arguments;
     var argc = arguments.length;
     var expires = (argc > 2) ? argv[2] : null;
     var path = (argc > 3) ? argv[3] : '/';
     var domain = (argc > 4) ? argv[4] : null;
     var secure = (argc > 5) ? argv[5] : false;
     document.cookie = name + "=" + escape (value) +
       ((expires == null) ? "" : ("; expires=" + expires.toGMTString())) +
       ((path == null) ? "" : ("; path=" + path)) +
       ((domain == null) ? "" : ("; domain=" + domain)) +
       ((secure == true) ? "; secure" : ""); // secure值为true时，在http中是无效的；在https中才有效
};
// cookie获取
Cookies.get = function(name){
    var arg = name + "=";
    var alen = arg.length;
    var clen = document.cookie.length;
    var i = 0;
    var j = 0;
    while(i < clen){
        j = i + alen;
        if (document.cookie.substring(i, j) == arg)
            return Cookies.getCookieVal(j);
        i = document.cookie.indexOf(" ", i) + 1;
        if(i == 0)
            break;
    }
    return null;
};
// cookie删除
Cookies.del = function(name) {
  if(Cookies.get(name)){
    var expdate = new Date();
    expdate.setTime(expdate.getTime() - (86400 * 1000 * 1));
    Cookies.set(name, "", expdate);
  }
};

来自： js中的cookie操作