js根据cookie名字获取cookie的方法

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;

}