JS.TS.NO.EXPLICIT.ANY
Disallow usage of 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.
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.
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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 (https://www.typescriptlang.org/docs/handbook/basic-types.html#any)