var str = "user=true;auth=openid;location.href='https://vk.com/auth/jDHSHjk=089&jhGAJ99aU-_83jhASIhdisajoidsa'";
var res = str.substring(str.indexOf("href='")+6, str.length-1);
alert(res);
var str = "user=true;auth=openid;location.href='https://vk.com/auth/jDHSHjk=089&jhGAJ99aU-_83jhASIhdisajoidsa'";
var result = /'([^']+)/.exec(str)[1];
alert(result);