JS工具类的一个详细介绍，如何操作Cookie

/***
	*读取指定的Cookie值 readCookie("id");
	*@param {string} cookieName Cookie名称
	*/
	function readCookie(cookieName) {
	 var theCookie = "" + document.cookie;
	 var ind = theCookie.indexOf(cookieName);
	 if(ind==-1 || cookieName=="") return "";
	 var ind1 = theCookie.indexOf(';',ind);
	 if(ind1==-1) ind1 = theCookie.length;
	 /*读取Cookie值*/
	 return unescape(theCookie.substring(ind+cookieName.length+1,ind1));
	}
	
	/***
	* 设置Cookie值 setCookie("id",1);
	* @param {string} cookieName Cookie名称
	* @param {string} cookieValue Cookie值
	* @param {number} nDays Cookie过期天数
	*/
	function setCookie(cookieName, cookieValue) {
	 /*当前日期*/
	 var today = new Date();
	 /*Cookie过期时间*/
	 var expire = new Date();
	 /*如果未设置nDays参数或者nDays为0，取默认值1*/
	 //if(nDays == null || nDays == 0) nDays = 1;
	 /*计算Cookie过期时间【 3600000 * 24 为一天】*/
	 expire.setTime(today.getTime() + 400000); //5分钟
	 document.cookie = cookieName + "=" + escape(cookieValue) + ";expires=" + expire.toGMTString();
	}
	
	/***
	* 删除cookie中指定变量函数 
	* @param {string} $name Cookie名称
	*/ 
 function deleteCookie($name){ 
 var myDate=new Date(); 
 myDate.setTime(-1000);//设置时间 
 document.cookie=$name+"=''; expires="+myDate.toGMTString(); 
 }
	
	/***
	* 删除cookie中所有定变量函数 
	* @param {string} cookieName Cookie名称
	* @param {string} cookieValue Cookie值
	* @param {number} nDays Cookie过期天数
	*/ 
 function clearCookie(){ 
 var myDate=new Date(); 
 myDate.setTime(-1000);//设置时间 
 var data=document.cookie; 
 var dataArray=data.split("; "); 
 for(var i=0;i<dataArray.length;i++){ 
 var varName=dataArray[i].split("="); 
 document.cookie=varName[0]+"=''; expires="+myDate.toGMTString(); 
 } 
 }