eslint/no-duplicate-case Correctness

✅ This rule is turned on by default.

What it does

Disallow duplicate case labels

Why is this bad?

If a switch statement has duplicate test expressions in case clauses, it is likely that a programmer copied a case clause but forgot to change the test expression.

Example

Examples of incorrect code for this rule:

var a = 1,
  one = 1;
switch (a) {
  case 1:
    break;
  case 2:
    break;
  case 1: // duplicate test expression
    break;
  default:
    break;
}

switch (a) {
  case one:
    break;
  case 2:
    break;
  case one: // duplicate test expression
    break;
  default:
    break;
}

Examples of correct code for this rule:

var a = 1,
  one = 1;
switch (a) {
  case 1:
    break;
  case 2:
    break;
  default:
    break;
}

switch (a) {
  case "1":
    break;
  case "2":
    break;
  default:
    break;
}

How to use

To enable this rule in the CLI or using the config file, you can use:

CLI

oxlint --deny no-duplicate-case

Config (.oxlintrc.json)

{
  "rules": {
    "no-duplicate-case": "error"
  }
}

References

• Rule Source