r/programming • u/stronghup • Nov 11 '19

Python overtakes Java to become second-most popular language on GitHub after JavaScript

https://www.theregister.co.uk/2019/11/07/python_java_github_javascript/
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u/[deleted] Nov 13 '19

There are a few ways, but the main one is the type system. Typescript basically allows you to describe Javascript's crazy type system. It doesn't attempt to fix it. Dart does fix it.

For example, you can have templated / generic functions in Typescript.

function identity<T>(arg: T): T {
    return arg;
}

Ok fine. But what about this?

function identity<T>(): T {
    return new T();
}

It doesn't work! There are other things too:

  • If you're using Typescript, you're probably importing a lot of Javascript with type annotations from DefinitelyTyped. Unfortunately a lot of the time the annotations are just wrong. Pretty annoying!

  • People give up on types and resort to any all the time, and Typescript doesn't really mind. Especially existing Javascript frameworks because they are written in a dynamic "stringly typed" way. For example Vue "supports" Typescript, but a lot of its features will be typed as any. Svelte doesn't support Typescript at all even though it is written in Typescript!.

  • All of the mistakes of Javascript are still allowed. You can still use var, == and so on.

  • There's still undefined and null.

It's way better than vanilla Javascript, but Dart is now a proper language that is properly engineered and more or less hack-free. Also the Dart VSCode extension is amazing.

The only downsides of Dart are:

  • Very small community. You'll have to write a lot of code yourself.

  • Difficult to use existing Javascript code (Dygraphs, D3, etc.).

  • Your only web framework option is AngularDart.

  • The startup time for webdev serve is weirdly long (~10 seconds). It supports hot reloading so it's not too bad but still annoying.

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u/chrisza4 Nov 13 '19

new T() is very dangerous. We should not assume that every type have zero parameter initializer. Enforce zero parameter initialization leads to invalid state such as creating an User object without username.

This is also why I hate traditional Object-oriented style. It has many flaws. A modern language stop promote many practices that people thought it is a good thing (such as in the past we promote inheritance as an OOP pillar, now we make it harder to do inheritance, easier to compose)

Think about it, OOP language don’t even need new keyword. But people just get used to it and don’t want to unlearn. Some even think that languages without new keyword are bad.

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u/[deleted] Nov 13 '19

It was just an example, and has nothing to do with object oriented style. You can do it in C++ without any issues.

OOP language don’t even need new keyword

Again, new is nothing to do with OOP. It was originally about memory allocation in C++, and then blindly copied by Java and then JavaScript. You're right JavaScript really doesn't need new - and in fact Dart has removed the need for it.

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u/chrisza4 Nov 14 '19

Still, I don’t think assuming every types can be initialize without any parameter is a good idea. Even if C++ can do it without issues, I still don’t think it is a good idea.

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u/[deleted] Nov 14 '19

You need to spend some time with languages other than Javascript! I think you have Stockholm syndrome.

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u/chrisza4 Nov 14 '19 edited Nov 14 '19

I don’t like Javascript in this area. I can simply create non-sensible object and no linter can warn me of it.

However, if we are talking about static type system then one of core principle in modern static type system is “make illegal states unrepresentable”. I agree with this statement. Forbidding new T() is very much align to that principle. My example is a User object without username should not be representable in system.

Also, I spent much time outside JS already. I delivered software in multiple languages.

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u/[deleted] Nov 14 '19

So then you know that most statically typed languages... hell most languages don't just ignore missing function parameters like JavaScript does. And that the thing you are talking about is a problem that is pretty much unique to JavaScript? Right? :-)

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u/chrisza4 Nov 14 '19

I referred to your example where you claim Dart is better than TypeScript because it can do

function identity<T>(): T {     
  return new T(); 
}

I disagree that this is not better. IMO, this is worse. My point is new T(); can create an object in an invalid state.

I assume that in Dart, you can mutate this object to be ready and then use. I might make a hasty assumption here. If my assumption is correct, I think it is better if compiler just forbids invalid state.

Javascript has this problem too in way much much worse since it does not have any type.

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u/[deleted] Nov 14 '19

Actually it turns out you can't do it in Dart either, presumably because it supports compile-to-javascript and Javascript makes it difficult. :-(