default-case
Some coding conventions require that all switch statements have a default case, even if empty.
Rule Type: Suggestion
Fixable: No
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.
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
switch (a) {
case 1:
/* code */
break;
}
Correct Code
// 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
Type: string (regex)
Default: /^no default$/i
Customize the comment pattern that indicates an intentional omission:
{
"rules": {
"default-case": ["error", {
"commentPattern": "^skip\\sdefault"
}]
}
}
switch(a) {
case 1:
/* code */
break;
// skip default
}
switch(a) {
case 1:
/* code */
break;
// skip default case
}
Best Practices
Explicit Default Handling
Even if the default does nothing, make it explicit to show it was considered.
// 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
// Handle unexpected values
switch (status) {
case 'pending':
showPending();
break;
case 'completed':
showCompleted();
break;
default:
throw new Error(`Unknown status: ${status}`);
}
Logging Unknown Cases
// 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.