---
url: /docs/guide/usage/linter/rules/import/unambiguous.md
---

### What it does

Warn if a `module` could be mistakenly parsed as a `script` instead of
as a pure [ES module](https://nodejs.org/api/esm.html#modules-ecmascript-modules).

### Why is this bad?

For ESM-only environments, ambiguous files may lead to unexpected results and problems.

### Examples

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

```js
function x() {}

(function x() {
  return 42;
})();
```

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

```js
import "foo";
function x() {
  return 42;
}

export function x() {
  return 42;
}

(function x() {
  return 42;
})();
export {}; // simple way to mark side-effects-only file as 'module' without any imports/exports
```

## How to use

## Version

This rule was added in v0.11.1.

## References