Redirect all traffic to root of another domain

Put this code in your ROOT .htaccess on www.old.com

Options +FollowSymLinks -MultiViews
RewriteEngine on

RewriteCond %{HTTP_HOST} ^(www\.)?old\.com$ [NC]
RewriteRule ^ http://www.new.com/ [R=301,L]

This rule will externally redirect all www.old.com/* to www.new.com/

From http://www.webconfs.com/how-to-redirect-a-webpage.php I'd say you can use the following configuration

Don't redirect subfolders/files (as you wanted): www.example.com/demo/ -> www.newexampledomain.com

Options +FollowSymLinks
RewriteEngine on
RewriteRule (.*) http://www.newdomain.com/ [R=301,L]

Redirect to subfolders/files: www.example.com/demo/ -> www.newexampledomain.com/demo/

Options +FollowSymLinks
RewriteEngine on
RewriteRule (.*) http://www.newdomain.com/$1 [R=301,L]

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