# default-case

> Require a `default` case in every `switch`

A `switch` without `default` does nothing when no `case` matches. When a new value shows up, it's silently skipped. A `default` makes you decide what happens then, even if the answer is to throw.

If you leave it out on purpose, say so with a `// no default` comment after the last `case`.

{/* Generated by src/codegen/lint-rule-docs.ts. Do not edit this section. */}

## Configure

Off by default. To turn it on:

```toml bunfig.toml
[lint.rules]
"default-case" = "error" # or "warn"
```

Every option, set to its default. The ones that are commented out are unset by default.

```toml bunfig.toml
[lint.rules]
"default-case" = ["error", {
  # commentPattern = <string>,
}]
```

{/* End of the generated section. */}

## Examples

Reported:

{/* bad */}
```js
switch (status) {
  case "open":
    show();
    break;
  case "closed":
    hide();
    break;
}
```

Not reported:

{/* good */}
```js
switch (status) {
  case "open":
    show();
    break;
  case "closed":
    hide();
    break;
  default:
    throw new Error("Unknown status: " + status);
}
```

{/* good */}
```js
switch (status) {
  case "open":
    show();
    break;
  case "closed":
    hide();
    break;
  // no default
}
```

## Options

| Option | Default | What it does |
| --- | --- | --- |
| `commentPattern` | `"^no default$"`, in any case | A regular expression for the comment that excuses a missing `default`. It's tested against the last comment after the last `case`. |

{/* good {"options": [{"commentPattern": "^skip default"}]} */}
```js
switch (status) {
  case "open":
    show();
    break;
  // skip default: other statuses are not shown
}
```

With your own pattern, `// no default` no longer counts:

{/* bad {"options": [{"commentPattern": "^skip default"}]} */}
```js
switch (status) {
  case "open":
    show();
    break;
  // no default
}
```

## When not to use it

In TypeScript, `@typescript-eslint/switch-exhaustiveness-check` reports every member of a union that has no `case`. It finds a new value when you lint. A `default` only finds it when the code runs.