Everyone loves TypeScript. It “solves” many problems JS has, it is a “superset” of JS, it will make your code error-prone and pleasant to read. There are a lot of good reasons to use TypeScript, but I am going to give you 7 really good reasons not to.
It is risky
Wow. How can it be risky, if TypeScript adds type definitions and checks them at compile time? As well as IDE integration will warn you about any type mismatches? Exactly because of that. TypeScript will only check types at compile time and only types that are available. Any network calls, system libraries, platform-specific APIs and non-typed third-party libraries have no way of communicating with TypeScript. As you get used to having your types checked and not having to fully understand the code and the platform, errors and bugs will manifest themselves.
With JS, you make no assumptions about types, and you check the concrete value of the variable to make sure it is what you expect it to be. Or, if you do not care about its type in this particular case, you do not. In TS, you rely on the compiler to do it for you, but it can only check so much. You can combine the two ways, but what is the point then? If you will spend time writing definitions and then spend time writing code to ensure these definitions are maintained during runtime, why have them in the first place?
It is messy
Another paradox: the language that was supposed to bring clarity and readability to the codebase obscures it instead. To show you what I mean, check out some of these examples I found in popular open-source libraries:
This one is from the Redux library, and all these 4 lines do is assign
Next example if from the RxJS library. I do not know about you, but if I have to fight a tool that is supposed to help me, I do not think this is a good tool.
It does not solve the problem
NaN === NaN being false, semicolons being optional or not optional, a linebreak changing an object definition into a scope, syntactic sugar in place of OOP are indeed problems. TypeScript does nothing to solve them, but introduces yet another standard, further polarizing the JS community.
Even under the assumption that the lack of typing in JS is a problem, TS does not solve it. Do you know what does? Java, C, C# and other compiled languages. They can safely guarantee strong typing at compile time and runtime. Interpreted languages are just not capable of it.
It is not a superset, it is a subset
It is open-source, but nothing more
Many reasons for using TypeScript state that it is open-source. That is true, TS compiler is distributed under MIT license. But it is still controlled by Microsoft, a giant monopolistic corporation, and its open-source advancements are nothing but a marketing move. Do not confuse open-source with democracy: Microsoft is still free to do anything you want with TS, and you are just here to watch. JS, on the other hand, is governed by an international committee and will not change anything without the community’s approval.
But big companies use it…
I cannot believe that some people consider this a reason. Big companies also use legacy codebases, commit tax frauds and discriminate against women. Why all of a sudden them using TypeScript is a good example?
But it has more features…
Not anymore. True, when TS was first introduced in 2012, it had features like classes, still not available in JS. But JS had come a long way since then, and now TS is struggling to keep up. If there is anything missing in JS, there is a babel plugin to do it.