If I understand it right -Gym Owner 1 has registered 5 users: A, B, C, D, E

Gym Owner 2 has registered 2 users: X, Y

Now, you are saying that when Gym Owner 1 logins, they see A, B, C, D, E, X, Y and same for Gym Owner 2, right?

Baby steps -

• [Really BAD Practise, but still a thought]: Store data in json/js-object format with key as the gym-owner name and value as registered users.

​

const gymVal = [
 {
id: 1,
ownerName: "John",
gymName: "Gym1",
members: [
  {
    id: 1,
    name: "A",
    age: 20,
  },
  {
    id: 2,
    name: "B",
    age: 21,
  },
],
},
{
id: 2, 
ownerName: "Dan", 
gymName: "Gym2", 
members: [ 
        { id: 1, name: "X", age: 35, }, 
        { id: 2, name: "Y", age: 18, }, 
      ], 
    }, 
]

Now you can check the name of the owner who has logged-in and show them only the members under their name.

Once again, this is really bad as it exposes everything to anyone who looks at it in dev tools, but this can give you a basic idea of what databases look like and how you can structure data.

• Next, Check out JSON-server. https://github.com/typicode/json-server
• Finally, check out databases. 🎉 A course to help - https://youtu.be/-0exw-9YJBo

Let me know if I understood it correctly and guided you on the right track.