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no-unused-private-class-members

Disallow unused private class members.

🧱

This is an "extension" rule that replaces a core ESLint rule to work with TypeScript. See Rules > Extension Rules.

This rule extends the base no-unused-private-class-members rule from ESLint core. This rule extends the base eslint/no-unused-private-class-members rule. It adds support for members declared with TypeScript's private keyword.

How to Use​

eslint.config.mjs
export default tseslint.config({
  rules: {
    // Note: you must disable the base rule as it can report incorrect errors
    "no-unused-private-class-members": "off",
    "@typescript-eslint/no-unused-private-class-members": "error"
  }
});

Try this rule in the playground ↗

Options​

See eslint/no-unused-private-class-members's options.

This rule has no options.

Examples​

class A {
  private foo = 123;
}
Open in Playground

Limitations​

This rule does not detect the following cases:

(1) Private members only used via a variable that would require type analysis to resolve the type.

type T = Foo;
class Foo {
  private prop = 123;

  method1(a: Foo) {
    // ✅ Detected as a usage
    const prop = this.prop;

    // ✅ Detected as a usage (variables with explicit and simple type annotations are handled)
    const otherProp = a.prop;
  }

  method2(a: T) {
    // ❌ NOT detected as a usage (complex type annotation that requires type information to handle)
    const prop = a.prop;
  }
}

(2) Usages of the private member outside of the class:

class Foo {
  private prop = 123;
}

const instance = new Foo();
// ❌ NOT detected as a usage
console.log(foo['prop']);

(3) Reassignments of this multiple times:

class Foo {
  private prop = 123;

  foo() {
    const self1 = this;
    const self2 = self1;
    return self2.prop;
  }
}

(4) Mutable reassignments of this:

class Foo {
  private prop = 123;
  private parent: Foo | null;

  foo() {
    let self = this;
    while (self.parent != null) {
      self = self.parent;
    }
    return self.prop;
  }
}

When Not To Use It​

If you don't want to be notified about unused private class members, you can safely turn this rule off.

Resources​

Taken with ❤️ from ESLint core.