server {
        listen       80;
        server_name  site.ru;
        location ~ ^/forum/(.*)$ {
          return 301 http://newsite.su/$1$is_args$args; 
        }

        location / {
          return 301 http://newsite.su/; 
        }
}

var i = array1.filter(al => {return !array2.map(bl => bl.id).includes(al.id)});

array1.filter(al => {return !array2.map(bl => bl.id).includes(al.id)}).map(l => l.id)