Change pricing without changing code

function canAccessFeature(user, usage) {
  // grandfather old pricing before April 2023
  const isGrandfathered = new Date(user.signupDate) < new Date("2023-04-01");

  // Pro plan logic
  if (user.plan === "pro") {
    if (isGrandfathered) {
      return usage < 200; // old limit
    } else {
      return usage < 100; // new limit
    }
  }

  // Starter plan logic
  if (user.plan === "starter") {
    if (isGrandfathered) {
      return usage < 50;
    } else {
      return usage < 25;
    }
  }

  // Lifetime deal logic
  if (user.plan === "lifetime") {
    return usage < 75;
  }

  // Trials get limited access
  if (user.plan === "trial") {
    return usage < 10;
  }

  // default deny
  return false;
}