function getCookie(cookieName) {
var allcookies = document.cookie;
var cookiePos = allcookies.indexOf(cookieName); //索引的长度
if (cookiePos != -1) {
// 把cookie_pos放在值的开始,只要给值加1即可。
cookiePos += cookieName.length + 1;
var cookieEnd = allcookies.indexOf(";", cookiePos);
if (cookieEnd == -1) {
cookieEnd = allcookies.length;
}
var value = decodeURI(allcookies.substring(cookiePos, cookieEnd));
}
return value;
}