---
url: /docs/guide/usage/linter/rules/eslint/no-duplicate-case.md
---

### 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.

### Examples

Examples of **incorrect** code for this rule:

```js
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:

```js
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

## Version

This rule was added in v0.0.3.

## References