Is TypeScript Worth It?

TypeScript is growing rapidly: it is now the 7th most popular language on GitHub, recently overtaking PHP. TypeScript is “JavaScript that scales”, which is an excellent marketing tagline. That’s an opportunity to work on a critical developer skill: thinking critically about marketing taglines. There’s always more nuance to a technical subject than you can fit in a pithy slogan.

TypeScript is all about static typing. In other words, TypeScript can help guarantee your code is internally consistent in terms of passing the right values to function signatures, but it is limited in the sense that it doesn’t necessarily check the input to your system. For example, below is a TypeScript Express server.

If you send a JSON body `{“a”:1}` to the above server using Postman or a similar HTTP client, the server will crash. The reason is simple: `req.body` can be anything at runtime because you can send any data you want in the HTTP request body.

This limitation is not news to experienced TypeScript developers. But it does provide some insight into where TypeScript provides value.

TypeScript does have some serious advantages when you have a large team working on a single codebase. Vue is a great example of a project that benefits from TypeScript: numerous core contributors, lots of outside contributors.

However, the reason why TypeScript works well for Vue is that Vue is a single project where the primary interface between Person A’s code and Person B’s code is a function signature. TypeScript can check the function signature and find cases where changes are incompatible.

On the other hand, suppose you’re an individual contributor building a Node.js microservice that primarily consumes data generated in a different programming language. This is an example where TypeScript doesn’t provide much value: the primary interface between your code and other people’s code is a network call where TypeScript can’t ensure compatibility between caller and callee.

How valuable TypeScript is depends on how your code primarily interfaces with other people’s code. If via function calls, then TypeScript is more valuable. If via network requests, then less valuable.