TypeScript is a Lie

Look, I love TypeScript. I really do. I use it on nearly every project. But after years of writing production code, architecting systems for Fortune 500 companies, and debugging disasters at 3 AM, I have come to an uncomfortable truth: TypeScript is a lie.

Not a malicious lie. More like the kind your parents told you about Santa Claus - well-intentioned, comforting, and ultimately designed to make your life better. But a lie nonetheless.

The Fundamental Lie

Here is the truth that every TypeScript developer eventually discovers, usually while staring at a production error that should have been "impossible":

TypeScript types do not exist at runtime.

When your beautifully typed code compiles down to JavaScript and runs in a browser or Node.js, all those elegant interfaces, strict type guards, and carefully crafted generics vanish into thin air. At runtime, JavaScript does not care about your types. It never did, and it never will.

It is like spending hours building an elaborate security system for your house, only to realize the walls are made of cardboard.

How TypeScript Has Betrayed Me (A Love Story)

Let me count the ways.

Betrayal 1: The API Response That Does Not Care About Your Interface

You have written the perfect interface:

interface User {
  id: number;
  email: string;
  createdAt: Date;
}

You call your API. You assign the response to your User type. TypeScript smiles and gives you a green checkmark. You feel safe. You feel secure.

Then, at runtime, the API returns this:

{
  "id": "not-a-number",
  "email": null,
  "createdAt": "2024-13-45T99:99:99"
}

TypeScript says nothing. Your application explodes. Your users are angry. Your manager is confused. "But I thought we used TypeScript?" they ask.

Welcome to the first betrayal.

Betrayal 2: JSON.parse Returns 'any' and Laughs at You

Consider this completely reasonable code:

const userData: User = JSON.parse(apiResponse);

TypeScript looks at this and says, "Sure, looks good to me!" But JSON.parse returns any. It has no idea what is in that string. It could be a User. It could be a Pizza. It could be the complete works of Shakespeare encoded as a number.

You have told TypeScript to trust you. And TypeScript, bless its heart, does.

Betrayal 3: The 'any' Escape Hatch We All Use

We all pretend we never use any. We judge code reviews where we see it. We write linting rules to prevent it.

And then we hit a deadline.

"I will come back and fix this later," we tell ourselves, adding as any to silence the compiler. We never come back. The any stays. It spreads. Soon, half your codebase is full of any, and your "type-safe" application is about as safe as a screen door on a submarine.

Betrayal 4: Third-Party Libraries with Lies of Their Own

You install a popular npm package. It has TypeScript definitions. You trust it.

Then you discover the types are incomplete. Or wrong. Or they were correct three versions ago but the library changed and the types did not.

Now you are maintaining type definitions for someone else's code. This was not in the job description.

Betrayal 5: Type Assertions Let You Lie to the Compiler

Type assertions are TypeScript's way of saying, "Okay, if you are really sure..."

const user = data as User;

This does not validate anything. It does not check anything. It is pure faith. You are telling TypeScript to believe you, and TypeScript has no choice but to comply.

It is like a doctor asking, "Are you sure you are not having a heart attack?" and accepting "Yes, I am sure" as a medical diagnosis.

The Type Safety Illusion

Here is the dirty secret about TypeScript: its safety is entirely opt-in.

You can write TypeScript that is nearly as safe as statically-typed languages like C# or Java. Or you can write TypeScript that is basically JavaScript with extra steps. The language does not force you to choose the safe path - it just makes the safe path available if you want it.

The problem is that "type safety" sounds absolute. It sounds like the compiler is protecting you. And it is - but only from the specific types of errors the compiler can detect at compile time.

Runtime errors? Data validation? Making sure the JSON from your API matches your interface? That is on you.

Why I Still Use TypeScript (Despite Everything)

After all these complaints, you might think I hate TypeScript. I do not. I genuinely love it. Here is why:

The IDE Experience is Incredible

Autocomplete that actually knows what properties exist. Refactoring that does not break everything. Immediate feedback when you misspell a property name. These quality-of-life improvements are worth the price of admission alone.

Self-Documenting Code

When I return to code I wrote six months ago, TypeScript interfaces tell me immediately what data structures I was working with. Without types, I would be reading implementation code and making educated guesses.

Refactoring Confidence

Need to change a function signature? TypeScript will tell you every single place that breaks. Try doing that in vanilla JavaScript without grepping through thousands of files and hoping you found everything.

Catching Obvious Mistakes Early

Yes, TypeScript does not catch everything. But it catches the stupid mistakes - typos, wrong argument counts, accessing properties that do not exist. These are the bugs that waste hours of debugging time when they slip through.

Using TypeScript Honestly: Patterns That Acknowledge Reality

The trick to using TypeScript effectively is acknowledging its limitations rather than pretending they do not exist.

Runtime Validation at the Boundaries

Any data entering your system from the outside world - APIs, user input, file uploads - needs runtime validation. Not TypeScript types. Actual validation.

Libraries like Zod, io-ts, or even simple validation functions that throw errors. Your types should be derived from these validators, not the other way around.

import { z } from 'zod';

const UserSchema = z.object({
  id: z.number(),
  email: z.string().email(),
  createdAt: z.string().datetime()
});

type User = z.infer<typeof UserSchema>;

// Now this actually validates at runtime
const user = UserSchema.parse(apiResponse);

Strict Mode is Not Optional

Turn on strict mode in your tsconfig.json. Yes, all of it. strictNullChecks, noImplicitAny, strictFunctionTypes - everything.

If your codebase is too messy to enable strict mode, your codebase is too messy to trust, with or without TypeScript.

Treat 'any' as a Code Smell

Not forbidden - sometimes you genuinely need it. But any time you use any, you should be able to explain why. "I do not feel like fixing this" is not a valid reason.

Type Guards for Runtime Checks

Type guards let you bridge the gap between runtime and compile time:

function isUser(data: unknown): data is User {
  return (
    typeof data === 'object' &&
    data !== null &&
    'id' in data &&
    typeof data.id === 'number' &&
    'email' in data &&
    typeof data.email === 'string'
  );
}

It is verbose, but it actually checks things at runtime instead of just hoping.

The Wisdom from the Trenches

I have had conversations with developers who have been doing this far longer than I have. One architect I know - someone who has been writing code since the Timex Sinclair days, who has built systems for Fortune 500 companies and government agencies - puts it this way:

"TypeScript is a tool for developers, not a replacement for thinking. It catches the bugs that waste time, but it will not design your architecture for you. It will not validate your data for you. It will not make bad decisions good decisions."

This architect has worked on everything from early e-commerce platforms to modern serverless microservices on AWS GovCloud. He has seen dozens of languages and frameworks come and go. His approach to TypeScript is pragmatic: use it for what it is good at (developer experience, refactoring safety, self-documentation), but never assume it replaces runtime validation or sound architecture.

"The best TypeScript developers," he told me, "are the ones who understand JavaScript deeply and use TypeScript to enhance their workflow, not replace their judgment."

The Uncomfortable Truth About Modern Development

TypeScript is not unique in having limitations. Every tool, every framework, every language has trade-offs. The problem is not TypeScript itself - it is the expectation that any single tool can solve all our problems.

We want silver bullets. We want to believe that if we just adopt the right technology, our code will magically become bug-free and maintainable. TypeScript promises safety, and we want to believe that promise so badly that we ignore the fine print.

The fine print says: "Safety at compile time only. Runtime validation sold separately. Actual safety may vary based on developer discipline."

The Bottom Line

TypeScript is a lie in the sense that it promises type safety but delivers compile-time assistance. It is a lie in the sense that it creates an illusion of protection that disappears the moment your code runs.

But it is a useful lie.

Like most useful lies, the trick is knowing when to believe it and when to verify for yourself. Trust TypeScript to catch typos and refactoring errors. Do not trust it to validate API responses or protect you from malformed data.

Use TypeScript for what it is excellent at: making your development experience better, making your code more maintainable, and catching the obvious mistakes before they waste your time.

Just do not forget to add runtime validation at your system boundaries. Because when your production server crashes at 3 AM with a "Cannot read property 'email' of undefined" error, TypeScript will not be there to help you. It was never there at runtime in the first place.

That is the lie. And now you know.

So What Now?

If you are using TypeScript (and you probably should be), here is the action plan:

1. Add runtime validation at every system boundary - API responses, user input, configuration files, anything that comes from outside your code.
2. Enable strict mode if you have not already. Yes, it will break things. Fix them.
3. Treat types as documentation for developers, not as guarantees about runtime behavior.
4. Use type guards when you need to verify types at runtime.
5. Stop pretending 'any' does not exist in your codebase. Find it, understand why it is there, and decide if it really needs to be.

TypeScript is an excellent tool. It makes development faster, refactoring safer, and code more maintainable. Just remember what it actually does - and what it does not.

The lie is not malicious. But you still need to know the truth.