I work on the frontend team, and the server team has started using a different approach for API requests. They now require me to send a property with the specific fields I want to be returned in the response.

For example:

http.post(`/api/v1/users`, { requiredFields: [1, 2, 3] }) 
// The response will be [{ firstname, lastname, age }]
// This means that firstname is 1, lastname is 2, and so on.

I want to make the response type-safe based on the numbers I send.

Here’s a small function that simulates what I need to send and what I get:

function server(fields) {
  const allFields = {
    1: 'firstname',
    2: 'lastname',
    3: 'age',
    4: 'address',
    5: 'email'
  };

  const result = {};

  fields.forEach(field => {
    if (allFields[field]) {
      result[allFields[field]] = null;
    }
  });

  return result;
}

I thought of creating an interface, type, enum, or some schema, but I’m not sure how to integrate that into JavaScript.