no-extra-non-null-assertion

Disallow extra non-null assertions.

✅

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

🔧

Some problems reported by this rule are automatically fixable by the --fix ESLint command line option.

The ! non-null assertion operator in TypeScript is used to assert that a value's type does not include null or undefined. Using the operator any more than once on a single value does nothing.

.eslintrc.cjs

module.exports = {
  "rules": {
    "@typescript-eslint/no-extra-non-null-assertion": "error"
  }
};

Try this rule in the playground ↗

Examples

❌ Incorrect

const foo: { bar: number } | null = null;
const bar = foo!!!.bar;

function foo(bar: number | undefined) {
  const bar: number = bar!!!;
}

function foo(bar?: { n: number }) {
  return bar!?.n;
}

✅ Correct

const foo: { bar: number } | null = null;
const bar = foo!.bar;

function foo(bar: number | undefined) {
  const bar: number = bar!;
}

function foo(bar?: { n: number }) {
  return bar?.n;
}

Options

This rule is not configurable.

Resources

• Rule source
• Test source