# no-shadow-restricted-names

> Disallow variables named `undefined`, `NaN`, `Infinity`, `eval`, `arguments` or `globalThis`

`undefined`, `NaN` and `Infinity` look like keywords, but they're ordinary globals, so a variable or a parameter can take their name. After `const undefined = "none"`, every `value === undefined` in that scope compares with `"none"`.

The rule reports variables, parameters, functions, classes and imports with one of these names.

This rule is on by default.

{/* Generated by src/codegen/lint-rule-docs.ts. Do not edit this section. */}

## Configure

On by default as a warning. To turn it off:

```toml bunfig.toml
[lint.rules]
"no-shadow-restricted-names" = "off" # or "error"
```

Every option, set to its default:

```toml bunfig.toml
[lint.rules]
"no-shadow-restricted-names" = ["warn", {
  reportGlobalThis = true,
}]
```

{/* End of the generated section. */}

## Examples

Reported:

{/* bad {"count": 2} */}
```js
const undefined = "none";

function toNumber(text, NaN) {
  return text === "" ? NaN : Number(text);
}
```

Not reported:

{/* good */}
```js
const missing = "none";

function toNumber(text, fallback) {
  return text === "" ? fallback : Number(text);
}
```

A variable named `undefined` that never gets a value is allowed, because it's the same as the global:

{/* good */}
```js
var undefined;
```

## Options

| Option | Default | What it does |
| --- | --- | --- |
| `reportGlobalThis` | `true` | Also report `globalThis`. |

If your project has an ESLint config and ESLint 9 or older installed, the default is `false`, as it is there.

{/* bad */}
```js
const globalThis = window;
```

{/* good {"options": [{"reportGlobalThis": false}]} */}
```js
const globalThis = window;
```