New Jersey is one of the closest beaches to Philly. Do you have a specific beach you want to go to? Maybe Wildwood , it is pretty popular place to go and have fun on the boardwalk.
i have not decided yet, advice me
Depends on what you are looking to do. Do you like sunbathing, playing in the sand, going into shops on the boardwalk, eating, drinking, gambling. New Jersey beaches have everything from family friendly in Ocean City to adult only in Atlantic City.
i think i should go to NJ
New Jersey does have the best beach options and many places to explore. Some people also go to Deleware and other travel all the way to Maryland to go to a beach from Philly. 
How often do you visit beaches
Once or twice a year. Depending on what family and friends want to do. Do you plan on going to the beach with family or friends?
thats so nice. i have huge desire to go one of this holidays
Summer holiday's the beaches are packed but it is the best time to go. 
with this crucial period do you think people still go for such vacations?
Yes. People are still traveling regardless of current events. With the beach being an outside activity it is safer than an indoor activity.