no-explicit-any

Disallow the any type.

Using the any type defeats the purpose of using TypeScript. When any is used, all compiler type checks around that value are ignored.

Attributes

• Included in configs
  • ✅ Recommended
  • 🔒 Strict
• Fixable
  • 🔧 Automated Fixer
  • 💡 Suggestion Fixer
• 💭 Requires type information

Rule Details

This rule doesn't allow any types to be defined. It aims to keep TypeScript maximally useful. TypeScript has a compiler flag for --noImplicitAny that will prevent an any type from being implied by the compiler, but doesn't prevent any from being explicitly used.

❌ Incorrect

const age: any = 'seventeen';

const ages: any[] = ['seventeen'];

const ages: Array<any> = ['seventeen'];

function greet(): any {}

function greet(): any[] {}

function greet(): Array<any> {}

function greet(): Array<Array<any>> {}

function greet(param: Array<any>): string {}

function greet(param: Array<any>): Array<any> {}

✅ Correct

const age: number = 17;

const ages: number[] = [17];

const ages: Array<number> = [17];

function greet(): string {}

function greet(): string[] {}

function greet(): Array<string> {}

function greet(): Array<Array<string>> {}

function greet(param: Array<string>): string {}

function greet(param: Array<string>): Array<string> {}

Options

The rule accepts an options object with the following properties:

type Options = {
  // if true, auto-fixing will be made available in which the "any" type is converted to an "unknown" type
  fixToUnknown: boolean;
  // specify if arrays from the rest operator are considered okay
  ignoreRestArgs: boolean;
};

const defaults = {
  fixToUnknown: false,
  ignoreRestArgs: false,
};

ignoreRestArgs

A boolean to specify if arrays from the rest operator are considered okay. false by default.

Examples of incorrect code for the { "ignoreRestArgs": false } option:

/*eslint @typescript-eslint/no-explicit-any: ["error", { "ignoreRestArgs": false }]*/

function foo1(...args: any[]): void {}
function foo2(...args: readonly any[]): void {}
function foo3(...args: Array<any>): void {}
function foo4(...args: ReadonlyArray<any>): void {}

declare function bar(...args: any[]): void;

const baz = (...args: any[]) => {};
const qux = function (...args: any[]) {};

type Quux = (...args: any[]) => void;
type Quuz = new (...args: any[]) => void;

interface Grault {
  (...args: any[]): void;
}
interface Corge {
  new (...args: any[]): void;
}
interface Garply {
  f(...args: any[]): void;
}

Examples of correct code for the { "ignoreRestArgs": true } option:

/*eslint @typescript-eslint/no-explicit-any: ["error", { "ignoreRestArgs": true }]*/

function foo1(...args: any[]): void {}
function foo2(...args: readonly any[]): void {}
function foo3(...args: Array<any>): void {}
function foo4(...args: ReadonlyArray<any>): void {}

declare function bar(...args: any[]): void;

const baz = (...args: any[]) => {};
const qux = function (...args: any[]) {};

type Quux = (...args: any[]) => void;
type Quuz = new (...args: any[]) => void;

interface Grault {
  (...args: any[]): void;
}
interface Corge {
  new (...args: any[]): void;
}
interface Garply {
  f(...args: any[]): void;
}

When Not To Use It

If an unknown type or a library without typings is used and you want to be able to specify any.

Further Reading

• TypeScript any type