> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/eslint/eslint/llms.txt
> Use this file to discover all available pages before exploring further.

# default-case

> Require default cases in switch statements

# default-case

Some coding conventions require that all `switch` statements have a `default` case, even if empty.

<Note>
  **Rule Type:** Suggestion\
  **Fixable:** No
</Note>

## Why This Rule Exists

Always having a `default` case makes it clear whether the developer forgot to handle a case or intentionally has no default behavior.

```js theme={null}
switch (foo) {
    case 1:
        doSomething();
        break;
    case 2:
        doSomething();
        break;
    default:
        // do nothing
}
```

## Rule Details

This rule requires a `default` clause in `switch` statements. You can optionally include a `// no default` comment if there's no default case.

## Examples

### Incorrect Code

```js theme={null}
switch (a) {
    case 1:
        /* code */
        break;
}
```

### Correct Code

```js theme={null}
// With default case
switch (a) {
    case 1:
        /* code */
        break;
    default:
        /* code */
        break;
}

// With comment indicating intentional omission
switch (a) {
    case 1:
        /* code */
        break;
    // no default
}

switch (a) {
    case 1:
        /* code */
        break;
    // No Default
}
```

## Options

### `commentPattern`

**Type:** `string` (regex)\
**Default:** `/^no default$/i`

Customize the comment pattern that indicates an intentional omission:

```js theme={null}
{
  "rules": {
    "default-case": ["error", { 
      "commentPattern": "^skip\\sdefault" 
    }]
  }
}
```

**Examples with custom pattern:**

```js theme={null}
switch(a) {
    case 1:
        /* code */
        break;
    // skip default
}

switch(a) {
    case 1:
        /* code */
        break;
    // skip default case
}
```

## Best Practices

### Explicit Default Handling

<Tip>
  Even if the default does nothing, make it explicit to show it was considered.
</Tip>

```js theme={null}
// Good: Shows you thought about defaults
switch (userType) {
    case 'admin':
        grantAdminAccess();
        break;
    case 'user':
        grantUserAccess();
        break;
    default:
        // Unknown user type, no special access
        break;
}
```

### Error Handling in Default

```js theme={null}
// Handle unexpected values
switch (status) {
    case 'pending':
        showPending();
        break;
    case 'completed':
        showCompleted();
        break;
    default:
        throw new Error(`Unknown status: ${status}`);
}
```

### Logging Unknown Cases

```js theme={null}
// Log for debugging
switch (action.type) {
    case 'INCREMENT':
        return state + 1;
    case 'DECREMENT':
        return state - 1;
    default:
        console.warn(`Unknown action type: ${action.type}`);
        return state;
}
```

## When Not to Use It

Disable this rule if you don't want to require `default` cases or comments in `switch` statements.

## Related Rules

* [no-fallthrough](/rules/no-fallthrough)