Skip to content

noFallthroughSwitchClause

Diagnostic Category: lint/suspicious/noFallthroughSwitchClause

JavaScript (and super languages)

Since: v1.0.0

Sources:

Same as: no-fallthrough

Description

Disallow fallthrough of switch clauses.

Switch clauses in switch statements fall through by default. This can lead to unexpected behavior when forgotten.

The rule doesn’t take process.exit() in consideration.

Examples

Invalid

switch (bar) {
  case 0:
    a();
  case 1:
    b();
}

code-block.js:2:2 lint/suspicious/noFallthroughSwitchClause ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ This case is falling through to the next case.
  
    1 │ switch (bar) {
  > 2 │ 	case 0:
      │ 	^^^^^^^
  > 3 │ 		a();
      │ 		^^^^
    4 │ 	case 1:
    5 │ 		b();
  
  ℹ Add a break or return statement to the end of this case to prevent fallthrough.

Valid

switch (foo) {
  case 1:
    case 2:
    doSomething();
    break;
    case 3: {
        if (cond) {
            break;
        } else {
            break;
        }
    }
  case 4:
    doSomething();
}

How to configure

{
  "linter": {
    "rules": {
      "suspicious": {
        "noFallthroughSwitchClause": "error"
      }
    }
  }
}