Comment by chc | Hacker News Reader

Comment by chc | Hacker News Reader

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> It's one of the fastest dynamic languages in existence, considerably faster than e.g. Ruby and Python

I think this is kind of a question of what it means for a language to be fast. The big browser companies have poured a mind-blowing amount of resources into making their JavaScript engines fast. This has made these JavaScript engines faster than other implementations of slow languages that have not had similar resources devoted to performance. But this does not mean "JavaScript is fast" in the sense that the design of JavaScript readily enables good performance, and it doesn't make JavaScript fast relative to actually fast languages.

> Compared to what? It's a dynamic language.

JavaScript's type system is extraordinarily weak even compared to most popular dynamic languages. For example:

  $ python -c "print(1 + '1')"
  Traceback (most recent call last):
    File "<string>", line 1, in <module>
  TypeError: unsupported operand type(s) for +: 'int' and 'str'

  $ ruby -e "puts(1 + '1')"
  -e:1:in `+': String can't be coerced into Fixnum (TypeError)
	from -e:1:in `<main>'

  $ node -e "console.log(1 + '1')"
  11

> I think this is kind of a question of what it means for a language to be fast [...]

It's significantly faster than most other dynamic languages. It's fast as a compilation target to the extent we can run Unreal Engine in the browser. So I consider the original comment I replied to that simply stated 'Bad performance' incorrect or at least lazy/contextless criticism. If you want to reframe, fine, but I'm not going there :)

Accidental string coercion is a valid point. Also hasn't bitten me in ~10 years of building large JS apps. And JS has many advantages over e.g. Python these days that to me vastly overshadow that downside (better support for FP for one).

(And if you really want that type safety you can use TypeScript, just another great thing to come out of the JS community, you know the one that GPP criticised for daring to provide choice).

> It's significantly faster than most other dynamic languages. It's fast as a compilation target to the extent we can run Unreal Engine in the browser. So I consider the original comment I replied to that simply stated 'Bad performance' incorrect or at least lazy/contextless criticism.

The entire point of my comment is that the statement "JavaScript is faster than other dynamic languages" is lazy/contextless praise.

V8 is fast. Rhino is slow. JScript 5 is really slow. They are all JavaScript. V8 is fast because people really wanted it to be fast and did some impressive cutting-edge work to make it happen, not because the language lends itself well to speed. It is a credit to the skill of the people working on the JavaScript engines that JavaScript programmers nowadays can enjoy decent speed, and AFAIK it's not particularly attributable to any specific features of the language.

I might want to read an article about a language that is fast in principle due to its specification. But the question that actually matters to me is: do actual implementations of a language's specification exist, that I can use, that are fast? The answer is yes for JS.

Whatever flaws JS clearly has, speed is not one of them. All the widely used implementations of the language are fast compared to similar languages.

I'm unsure why you think it matters that this speed came about due to hundreds of thousands of hours of work spent on optimizing various compiles and interpreters. I never see anyone saying "Boy SQL sure is fast, but only because so many intelligent people spent their careers making it fast, so it doesn't count."

Remember, this little argument started because someone described JavaScript as slow. That claim is incredibly disingenuous. No, JavaScript's speed isn't directly linked to the language spec but...who cares?

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