default-case

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.

Configure

Off by default. To turn it on:

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

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

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

Examples

Reported:

switch (status) {
  case "open":
    show();
    break;
  case "closed":
    hide();
    break;
}

Not reported:

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

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.

switch (status) {
  case "open":
    show();
    break;
  // skip default: other statuses are not shown
}

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

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.