Need help converting get_user_meta [keys] into own array

You have to return the keys from array with this:

$keys = array_keys($all_meta_for_user);

Afterwards, implode your array to a string (inserting a dot before to create the first class):

$stringedKeys=".".implode(',.', $keys);

And now you have a string of keys that you can use in JS if you like, or insert them from PHP directly.