cookieObj=function(){}
cookieObj.prototype.clearCookie = function() {
var now = new Date();
var yesterday = new Date(now.getTime() - 1000 * 60 * 60 * 24);
this.setCookie('co'+this.obj, 'cookieValue', yesterday);
this.setCookie('cs'+this.obj, 'cookieValue', yesterday);
};

// [Cookie] Sets value in a cookie
cookieObj.prototype.setCookie = function(cookieName, cookieValue, expires, path, domain, secure) {
document.cookie =
escape(cookieName) + '=' + escape(cookieValue)
+ (expires ? '; expires=' + expires.toGMTString() : '')
+ (path ? '; path=' + path : '')
+ (domain ? '; domain=' + domain : '')
+ (secure ? '; secure' : '');
};

// [Cookie] Gets a value from a cookie

cookieObj.prototype.getCookie = function(cookieName) {
var cookieValue = '';
var posName = document.cookie.indexOf(escape(cookieName) + '=');
if (posName != -1) {
var posValue = posName + (escape(cookieName) + '=').length;
var endPos = document.cookie.indexOf(';', posValue);
if (endPos != -1) cookieValue = unescape(document.cookie.substring(posValue, endPos));
else cookieValue = unescape(document.cookie.substring(posValue));
}
return (cookieValue);
};

// [Cookie] Returns ids of open nodes as a string
dTree.prototype.updateCookie = function() {
var str = '';
//找到需要修改的key值key
this.setCookie('co' +key , str);
};