TypeScript’s doomed embrace of JavaScript

Microsoft recently announced TypeScript. From what I can tell, it’s Javascript with optional types. The type annotation syntax is the same as in Adobe’s ActionScript and in the sadly defunct ECMAScript 4.

TypeScript also includes a new class syntax based on the one proposed in ECMAScript 6. I’m dubious about the addition of class-based features to Javascript. Javascript’s traditional strength is in prototypal inheritance and informal interfaces. I think there’s value in there being only one way to do things in a programming language.

As the Zen of Python puts it:

“There should be one– and preferably only one –obvious way to do it.”

And as Ruby’s designer Matsumoto describes the Principle of Least Astonishment:

“Everyone has an individual background. Someone may come from Python, someone else may come from Perl, and they may be surprised by different aspects of the language. Then they come up to me and say, ‘I was surprised by this feature of the language, so Ruby violates the principle of least surprise.’ Wait. Wait. The principle of least surprise is not for you only. The principle of least surprise means principle of least my surprise [sic]. And it means the principle of least surprise after you learn Ruby very well. For example, I was a C++ programmer before I started designing Ruby. I programmed in C++ exclusively for two or three years. And after two years of C++ programming, it still surprises me.”

I’ve written Perl, and I’ve written C++. Both of them are kitchen sink languages that allow for every possible way of doing things. Per the above, this is not a good thing. For a discussion of the problems with C++, try the C++ Frequently Questioned Answers (FQA).

I think adding classes to Javascript would detract from the beauty of the language, or at least the beauty of JavaScript’s Good Parts. I would suggest that a much more useful and Javascript-esque enhancement would be not adding classes, but rather adding Go-style interfaces.

TypeScript is unlikely to become any more successful than Google’s Dart, thought to give Microsoft credit TypeScript is a lot more compatible with the existing Javascript infrastructure. The only post-Javascript success story that I’m aware of is CoffeeScript, and CoffeeScript’s strength is that it does not seek to replace Javascript.

(On a side note, I found out about TypeScript from Eric Lippert’s How do we ensure that method type inference terminates?)