A police spokeswoman said about 6.50pm the man was at the centre to buy take-away food for his family when he asked two men and a woman if they would move from a vacant bay so that he could park in it.
She said they approached and one of the men threatened him before hitting him in the head with a bottle, which broke as the victim fell down, unconscious. The attackers fled on bicycles.
The spokeswoman said the victim suffered cuts on his face and head and was helped by witnesses at the scene then taken to Armadale hospital for treatment.
The male attacker was described as about 18, with dark skin.