Why would you NOT use TypeScript?

TypeScript has exploded in popularity in recent years as a typed superset of JavaScript that compiles to plain JavaScript. As of 2022, TypeScript is used by over 78% of developers according to the State of JS survey. There‘s no doubt that TypeScript offers many advantages – enhanced IDE support, earlier bug detection, safer refactoring, and improved readability and maintainability thanks to static types. The benefits of TypeScript are well-documented.

However, in the midst of all the TypeScript hype, it‘s worth asking the contrarian question – why would you NOT use TypeScript? Are there cases where sticking to vanilla JavaScript makes more sense? Let‘s explore some potential drawbacks and limitations of TypeScript that may have you second-guessing if it‘s the right fit for your project.

1. Extra compilation step

One of the biggest drawbacks of TypeScript is that it requires an extra build step to compile your TS code to regular JS. This means you can‘t just open an HTML file, write some TypeScript, and expect it to run in the browser. You‘ll need to set up a build process using something like webpack or Rollup to transpile the TypeScript to JavaScript.

This extra compilation step adds complexity to your development workflow. It‘s another potential point of failure. Compilation can be slow for large projects. And it‘s something else you need to manage and configure. With vanilla JS, you can just write code and run it directly without any extra hurdles.

2. Steep learning curve

If you‘re coming from a JavaScript background, getting up to speed with TypeScript can feel daunting. The type system introduces a bunch of new concepts and syntax – interfaces, enums, generics, union/intersection types, type guards, and more. The official TypeScript docs are not known for being the most beginner-friendly.

For experienced developers who are already familiar with typed languages like Java or C#, the learning curve may not be as steep. But for many web developers who got their start with vanilla JS, all the typing ceremony can feel like overkill and slow them down as they struggle to understand TypeScript‘s more advanced features. There‘s a risk that the complexity of the type system can act as a barrier for newcomers and actually make code harder to understand for those less familiar with TypeScript.

3. Slower development speed

In addition to the learning curve, many developers find that TypeScript slows down their raw coding speed, at least initially. With dynamic languages like JS, you can just start writing code and worry about the details later. But with TypeScript, you‘re constantly annotating types which can interrupt your flow.

Over time, the type annotations may become second nature and even enhance your productivity by catching type errors early. But in the short term, the extra keyboard strokes spent appeasing the type checker can feel like speed bumps slowing you down. Sometimes, the type inference doesn‘t work perfectly and you waste time trying to get the types to line up. Other times, you know the code will work but you still need to convince the overly pedantic compiler.

4. Incompatibility with some libraries

While most popular JS libraries now ship with TypeScript type definitions, not all libraries have 100% TS support. You may run into blurry type definition files marked with any. Or you may find TS definitions that are out-of-date compared to the latest version of the library.

This can lead to a frustrating experience where your technically valid JS code is not type checking because of incomplete or inaccurate type definitions from a third-party library. You‘re stuck using an old version or you have to resort to ugly workarounds like type assertions.

5. False sense of security

Once you‘ve spent hours appeasing the TypeScript compiler and you see those green squiggles vanish, it‘s easy to think your program is bulletproof. But it‘s critical to remember that TypeScript is only checking for type-related errors. There are countless other types of runtime errors that can still slip through – null pointer exceptions, off-by-one errors, logic bugs, etc.

It‘s dangerous to assume that a successful TypeScript compilation means your code is flawless. The type system can lull you into a false sense of security where you neglect other forms of testing because you assume the compiler will catch all errors. In reality, there‘s no substitute for a robust suite of unit tests and integration tests to verify program correctness. Don‘t let the type system become a crutch.

6. Painful migration

If you have a large, existing JavaScript codebase, migrating to TypeScript can be a massive undertaking. Unless you have a solid test suite, you‘ll likely be doing mostly manual conversion from JS to TS. Even with tests, there‘s always a risk of introducing new bugs during the conversion process.

The migration can take weeks or months depending on the size of your codebase. In the meantime, you‘re left with an awkward mix of JS and TS files. And everyone on your team needs to get up to speed with TypeScript or they won‘t be able to contribute. For many organizations, the costs may outweigh the benefits, at least in the short term. It‘s not an easy decision to migrate to TypeScript later in a project‘s lifecycle.

7. Alternative type systems

For some developers, it‘s not that they hate types, they just prefer a different flavor of types. TypeScript has some competition in the typed JavaScript space. The most notable alternative is Flow, an open-source static type checker developed by Facebook.

Flow and TypeScript have a lot in common. But Flow is considered simpler and easier to learn. It also requires less refactoring to adopt into an existing codebase because it allows you to mix untyped and typed code. You don‘t have to go all-in on types from day one.

Some developers find Flow‘s type inference to be a bit smarter than TypeScript‘s, requiring fewer manual annotations. Flow also has a few unique features like existential types and type coverage tracking. While TypeScript is more popular, Flow remains a viable option for those who want gradual typing without all of TypeScript‘s complexity.

8. "Plain ol‘ JavaScript is good enough"

There‘s a vocal segment of the JS community that argues you don‘t need types at all – plain old JavaScript is perfectly adequate if you follow best practices. These developers prefer the simplicity and flexibility of JS‘s dynamic types.

They argue that you can get many of the same benefits of static typing with tools like ESLint and by being disciplined about writing good tests. If you architect your code well with proper abstractions and SOLID principles, your vanilla JS code can be just as safe and maintainable as equivalent TypeScript.

Many purists believe that adding types is antithetical to the "JavaScript way". They cite large, successful JavaScript codebases like Google and Facebook that are mostly untyped. For these developers, the extra safety of TS isn‘t worth the complexity cost. They‘d rather embrace the dynamism of JS.

9. Non-type-related bugs

As mentioned earlier, TypeScript only catches type-related errors. But many common JS bugs are not due to type mismatches at all. Here are some examples of non-type-related bugs that TS can‘t save you from:

• Forgetting to handle a Promise rejection
• Mutating state accidentally
• Accessing a property on an undefined object
• Off-by-one errors in a for loop
• Incorrect business logic
• DOM and browser quirks
• NPM dependency vulnerabilities

The list goes on. The point is, even with 100% type coverage, TypeScript is not a panacea. It won‘t make your code magically bugproof. Don‘t expect it to be a silver bullet.

10. Subjective productivity benefits

At the end of the day, the pros and cons of TypeScript are highly subjective. While the main benefits of static typing are well established – earlier bug detection, safer refactoring, improved readability – the actual productivity impact is harder to quantify.

Numerous case studies from Airbnb, Lyft, Pinterest etc. report that migrating to TypeScript increased their productivity. But these results may not generalize to all teams. There‘s an argument that the initial cost of adopting TS cancels out the later productivity gains.

For some developers, the cognitive overhead of appeasing the type checker all the time is a net negative for productivity, slowing them down more than the type safety helps them. Especially for smaller, less complex projects, the juice may not be worth the squeeze. Your mileage may vary.

Conclusion

So, should you use TypeScript? Like most technical decisions in software engineering, the unsatisfying answer is: it depends. TypeScript is an incredibly powerful tool that offers significant benefits around type safety, tooling, and maintainability. For large codebases, the pros usually outweigh the cons.

But TypeScript is not a silver bullet. It doesn‘t absolve you from writing tests. It can‘t catch all bugs. It adds complexity and requires a build step. For small projects, the overhead may not be worth it. And some developers simply prefer the simplicity of vanilla JS. Weigh the tradeoffs carefully.

At the end of the day, the best language choice depends on your specific context – your team‘s skills, your project‘s requirements, your existing codebase. Don‘t adopt TypeScript just because it‘s trendy. Make an informed decision based on your constraints. And if you do use TypeScript, don‘t expect magic. Use it as one tool in your toolbelt, not as a crutch. Happy coding!