Does the divorce of an enraged person who told his wife "You are divorced" once online take effect, and is there a way to take back the wife without her family's knowledge?

If the divorce occurs before consummation and before seclusion, it is an irrevocable divorce according to the consensus of scholars, and resumption of the marriage is not permissible except with a new contract.

However, if the divorce occurs before consummation but after seclusion, the majority of jurists hold that it is an irrevocable divorce, and there is no returning to the marriage except with a new contract. In contrast, the Hanbalis are of the view that it is a revocable divorce, and the husband can take his wife back as long as she is within her waiting period (iddah). Adopting the view of the majority is more cautious. However, if the wife desires to return and the husband is of good character and religious commitment, then the Hanbali view might offer a way to return without a new contract, as long as she is within her iddah.

In summary: If there was no seclusion, there is no way to return except with a new contract. If there was seclusion and a desire to return, resumption of the marriage is possible without informing the family, provided the wife is within her iddah.