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Ensure Switch Cases End With an Unconditional "break" Statement

Medium
intentionality - clearMaintainability

What is it?​

This practice ensures that every switch case in your TypeScript code terminates with an unconditional statement such as "break". Failure to do so may result in unintended fall-through, where the execution unintentionally continues into the next case block.

Why apply it?​

Accidental fall-through in switch cases can lead to bugs that are hard to understand and maintain. By explicitly ending each case with a break (or an alternative unconditional control flow statement like return, throw, or continue when appropriate), you create clear, predictable, and maintainable code behavior.

How to Fix it?​

Audit your switch-case statements and verify that each case properly concludes with an unconditional termination statement (commonly "break"). If fall-through behavior is intended, make sure it is clearly documented by adding a comment like // fall through. For cases where control flow should exit the switch (via return, throw, etc.), ensure that the logic is explicit and unambiguous.

Examples​

Example 1:​

Negative​

Incorrect implementation that violates the practice.

switch (errorCode) {
  case 404:
    logClientError();
    alertUser("Client error occurred.");  // Noncompliant: Missing break causes fall-through.
  case 405:
    logClientErrorDetails();
    break;
  case 500:
    logServerError();
    alertUser("Server error occurred.");
    break;
  default:
    logUnknownError();
    alertUser("An unknown error occurred.");
    break;
}

Example 2:​

Positive​

Correct implementation following the practice.

let orderStatus = 'completed';

switch (orderStatus) {
  case 'pending':
    initiateOrderProcessing();
    notifyCustomer("Your order is pending.");
    break;
  case 'processing':
    updateOrderStatus();
    notifyCustomer("Your order is processing.");
    break;
  case 'completed':
    finalizeOrder();
    notifyCustomer("Your order is completed.");
    break;
  default:
    logError("Unknown order status encountered.");
    notifyCustomer("Order status error.");
    break;
}

Negative​

Incorrect implementation that violates the practice.

switch (userRole) {
  case 'admin':
    grantAdminPrivileges();
    logAccess('admin');
    break;
  case 'editor':
    grantEditorPrivileges();
    updateContent();  // Noncompliant: Missing break, causing fall-through.
  default:
    grantGuestPrivileges();
    logAccess('guest');
    break;
}

Example 3:​

Positive​

Correct implementation following the practice.

switch (errorCode) {
  case 404:
  case 405:
    logClientError();
    alertUser("Client error occurred.");
    break;
  case 500:
    logServerError();
    alertUser("Server error occurred.");
    break;
  default:
    logUnknownError();
    alertUser("An unknown error occurred.");
    break;
}

Negative​

Incorrect implementation that violates the practice.

let orderStatus = 'processing';

switch (orderStatus) {
  case 'pending':
    initiateOrderProcessing();
    notifyCustomer("Your order is pending.");
    break;
  case 'processing':
    updateOrderStatus();
    notifyCustomer("Your order is processing.");  // Noncompliant: Missing break causes fall-through.
  case 'completed':
    finalizeOrder();
    notifyCustomer("Your order is completed.");
    break;
  default:
    logError("Unknown order status encountered.");
    notifyCustomer("Order status error.");
    break;
}

Example 4:​

Positive​

Correct implementation following the practice.

switch (userRole) {
  case 'admin':
    grantAdminPrivileges();
    logAccess('admin');
    break;
  case 'editor':
    grantEditorPrivileges();
    updateContent();
    break;
  default:
    grantGuestPrivileges();
    logAccess('guest');
    break;
}