no-unsafe-unary-minus

Require unary negation to take a number.

✅

Extending "plugin:@typescript-eslint/recommended-type-checked" in an ESLint configuration enables this rule.

💭

This rule requires type information to run, which comes with performance tradeoffs.

TypeScript does not prevent you from putting a minus sign before things other than numbers:

const s = 'hello';
const x = -s; // x is NaN

This rule restricts the unary - operator to number | bigint.

Flat Config

eslint.config.mjs

export default tseslint.config({
  rules: {
    "@typescript-eslint/no-unsafe-unary-minus": "error"
  }
});

Legacy Config

.eslintrc.cjs

module.exports = {
  "rules": {
    "@typescript-eslint/no-unsafe-unary-minus": "error"
  }
};

Try this rule in the playground ↗

Examples

❌ Incorrect

declare const a: string;
-a;

declare const b: {};
-b;

Open in Playground

✅ Correct

-42;
-42n;

declare const a: number;
-a;

declare const b: number;
-b;

declare const c: number | bigint;
-c;

declare const d: any;
-d;

declare const e: 1 | 2;
-e;

Open in Playground

Options

This rule is not configurable.

When Not To Use It

Type checked lint rules are more powerful than traditional lint rules, but also require configuring type checked linting.

See Troubleshooting > Linting with Type Information > Performance if you experience performance degradations after enabling type checked rules.

Resources

• Rule source
• Test source