When to use any?

TypeScriptJunior~2 min read

When you CAN use `any`

Sometimes any is genuinely appropriate - as a temporary tool, not a permanent solution.

1. When the type is truly unknown (temporarily)

For example, you are parsing JSON from an external API that has no types yet:

javascript

let data: any = JSON.parse(response);

Later you can replace it with:

javascript

let data: unknown = JSON.parse(response);

and add checks - but at an early stage of development any is acceptable.

2. During quick debugging or prototyping

When you are just experimenting with logic or an API, and you need to "get it running somehow".

javascript

function debug(value: any) {
  console.log("Debug:", value);
}

The main thing is not to forget to later replace any with a real type.

3. When working with code that has no types

For example, a library has no .d.ts descriptions or is written in JavaScript.

javascript

const legacyLib: any = require("old-js-lib");
legacyLib.doSomethingWeird();

In this case any lets you work without compile errors until you write or install types (@types/...).

4. When the type is too complex and you know what you are doing

Sometimes TS's type system cannot handle extremely dynamic structures (for example, deeply nested generics). Then any can be a temporary "bypass" of the compiler:

javascript

const deepValue: any = getValueFromComplexStructure();

The main thing is to localize the use of any and not let it leak "outward".

5. In generic logs, tracing, telemetry

If a function just logs, without changing data, strict typing is not needed:

javascript

function logEvent(event: any) {
  console.log("EVENT:", event);
}

When you CANNOT use `any`

Here is where any turns from a convenience into a threat.

1. In application logic

If the variables involved in computations have type any, TypeScript stops protecting you from type errors.

javascript

let user: any = { name: "Tim" };
user(); // Runtime error - TS will not warn you

2. In API contracts

If a function is exported and used by other modules, any makes it unpredictable.

javascript

function getUser(id: any): any { ... }

Better:

javascript
function getUser(id: number): User { ... }

3. In public libraries

If you are writing an SDK or an NPM package, any kills all the benefit of TypeScript for your users. They lose autocomplete, hints, and type safety.

4. In large projects

any is like a virus: once it enters the type system, it spreads. Example:

javascript

function process(value: any) {
  return value; // returns any
}

const result = process("test");
result.toFixed(2); // Runtime error, but TS stays silent

Now result has also become any, and the whole chain loses typing.

5. When interacting with the DOM, APIs, and user data

Type errors often occur there, and any hides them. For example:

javascript

const el: any = document.getElementById("btn");
el.addEventListener("click", 123); // TS will not complain, but it will break at runtime

Summary

Scenario	Use `any`?	Alternative
Quick debugging / prototype	Temporarily okay	Replace later with a specific type
Library without `.d.ts`	Acceptable	`@types/...` or `unknown`
Processing external data	Temporarily	`unknown` + checks
API contracts, business logic	Not allowed	Strict interfaces
Public libraries	Not allowed	Universal generics
Large projects	Not allowed	`unknown` or precise types

Usage recommendations

Localize any - limit its scope (to one variable, not "down the chain").
Use as Type if you know the type and TypeScript could not infer it:

javascript
const data = JSON.parse(text) as User;
Enable strict flags in tsconfig.json:

javascript
{ "compilerOptions": { "noImplicitAny": true, "strictNullChecks": true, "strict": true } }

-> TypeScript will warn you if type any appears implicitly somewhere.

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