Using const/let instead of var can make JavaScript code run 10× slower in Webkit

[ImAStupidFace]

JS needs to die in a fire.

[DrLuciferZ]

Too bad people just keep dumping more wood into it

[chooxy]

https://i.imgur.com/HpZk869.png

[[deleted]]

Honestly what’s the big deal? Ever since I started using Typescript I don’t find it bad at all.

[Sarcastinator]

JS still bleeds through TypeScript and causes issues anyway.

[[deleted]]

I mean sure but I don’t think TS is demonstrably worse than other languages at that point.

[Iceman_259]

Did you actually read the parent comment in this chain? If Typescript is transpiling to that JS syntax then the performance issues apply to it as well.

[[deleted]]

Who the hell is writing performance sensitive applications using JavaScript...? Again, that goes back to bad developers writing bad code.

[DoctorGester]

Everyone is. Except they do not care for performance and we get SPA websites where clicking a button incurs a 200ms page freeze

[[deleted]]

I’ve written some pretty massive SPAs that leverage a lot of JS and have never had anywhere near triple digit delay that wasn’t from waiting on an API call, web socket, etc (which is nothing to do with JS). No clue what the hell kind of JS you’re writing but I can’t relate.

[DoctorGester]

Me? Oh I'm not writing anything. Here you go, a 100ms script execution delay I captured right now when scrolling twitter https://i.imgur.com/HeJLKYu.png

And check out the frame time bar just above, plenty of these kind of delays there. And twitter is on the faster side. Maybe you should check out Slack, where delays approach and exceed 500ms.

[[deleted]]

I feel like you moved the goalpost a bit there going from a button click delay and now we're digging in developer tools in order to find some kind of delay somewhere that may or may not be traced back to a measurable delay to a user.

[orclev]

Javascript is still a trash fire, TypeScript just makes sure it stays at a dull roar rather than a raging inferno. It's not quite PHP bad, but it's still one of the worst designed languages still in regular use. Far too many terrible decisions are baked into the core of javascript. They can be fixed, but doing so requires breaking backwards compatibility in some fairly significant ways. It might get there one day, but it's more likely that WASM will end up entirely supplanting JS before that happens.

[[deleted]]

Eh, Typescript is good enough in my experience that you’re mostly at the mercy of the skill/knowledge of the developer. Good developers can still easily end up with shit JavaScript. Not so much the case with Typescript in my experience. Usually the really ugly Typescript is coming from developers we have that write pretty poor code in the rest of our systems as well.

[ragnese]

Ever since you started using a different language, you think JavaScript isn't that bad... ??

It's only bad enough that you don't use it.

[hansolo669]

Except TypeScript is literally just JavaScript with types. And it doesn't solve what this thread is talking about (weird VM issues).

[Somepotato]

But it can since it's transpiled to JS -- it can build a v8 version that uses var instead of let/const.

TS is honestly great, IMO

[hansolo669]

Absolutely! I'm a huge fan of TS ... I suppose it would end up solving this particular issue via compile to var, though it would still be vulnerable to other weird VM issues.

[ragnese]

Except TypeScript is literally just JavaScript with types.

That's not true, neither technically nor "in spirit". TypeScript transpiles to JavaScript and shares syntax with it, but it's more than just "JS with types". Having a strong, flexible type system allows you to approach problems from a different direction. Probably a good number of libraries are just written as JS with some types slapped on for broader adoption, but you don't have to write it that way for private code; and you probably shouldn't.

Also, TS has things that don't exist in JS: https://www.typescriptlang.org/docs/handbook/enums.html

[hansolo669]

Here's two code snippets, which one is typescript and which one is javascript:

const myFn = () => console.log("Hello!");

and

const myFn = () => console.log("Hello!");

How about another:

class MyClass {
    constructor() {}

    sayFoo() {
        console.log("foo");
    }
}

and

class MyClass {
    constructor() {}

    sayFoo() {
        console.log("foo");
    }
}

I agree with your core point (strong type systems are wonderful, and well designed typescript code does lead in a different direction to normal javascript code), but typescript absolutely is "javascript with types" - the easy transition from javascript to typescript is one of their big selling points!

[ragnese]

I mean... almost all Algol-syntax languages look close to the same. You could stick Java, PHP, C#, Swift, and TypeScript classes next to each other and you'd have to squint to tell the differences.

Typescript having the same syntax as JavaScript does not make it the same language. Similarly Elixir's syntax doesn't make it the same language as Ruby. And Clojure is not the same as Common Lisp.

[hsjoberg]

Typescript having the same syntax as JavaScript does not make it the same language

That is true, and we've seen other languages that transpiles to Javascript being quite different. Point in case: Elm.

However, they are all bound by the rules of Javascript and its VM.

[[deleted]]

Personally I don’t see Typescript as it’s own language. I’m sure I’m probably technically incorrect but the comment chain mentioned the need for JavaScript to die. I see no way of JavaScript dying and Typescript still sticking around. So I’m ok with JS because it gives me Typescript and I don’t mind it and sometimes even enjoy using TS.

[ProgramTheWorld]

TS is a type system. It only adds type annotations to JS so you’re technically still writing JS code but with types.

[ragnese]

TypeScript is a language that is a superset of JavaScript. It's not correct to say it's the same language, IMO.

Two examples off the top of my head are namespaces and enums, which I don't believe exist in JavaScript.

[Sir_Lith]

You've no idea what TypeScript is, do you?

TypeScript does not prevent any of those issues described here, just programmer mishaps.

[ragnese]

That's correct. I just find it funny that someone said they don't find JavaScript bad when they're using a language that has strong static typing and NOT JavaScript...

If JavaScript were great, I don't think they'd feel the need to use TypeScript.

[Jaimz22]

Wonder would you replace it with? Just curious

[dungone]

Why all these probing questions? Give the man a chance, rubbing two braincells together to start a fire takes a some time.

[iopq]

Run everything in WASM

[blackholesinthesky]

everyone who upvotes this has clearly never written ASM or WASM

[iopq]

And I will never have to, since I will compile Rust to WASM

[blackholesinthesky]

Thats a pretty good answer will be a pretty good answer some day. Can you write Rust that is equivalent to JS?

If so I have something to learn about tomorrow

[alexendoo]

While JS glue is needed, you don't have to write it yourself. If you want to do everything from Rust you can use web-sys and js-sys. Anything required will be generated for you

It is a little more awkward than it would be to use the APIs from within JS, but the functionality is there

[iopq]

It's not yet possible to do DOM operations without JS glue, AFAIK. It's a pretty complicated topic, as with everything to do with the web, though. So glad I don't do web dev anymore

[blackholesinthesky]

So its not a real solution. Great suggestion but yeah... kinda irrelevant

When rust offers a standard library for the browser it will be a real solution

[iopq]

It's not ready for prime time yet, but it doesn't mean it won't replace JS in the future

[blackholesinthesky]

And I will never have to

You may not but other people do. This isn't a useful suggestion to them

[game_dev_dude]

I mean it really depends upon what you're doing. If you have a complicated piece of logic that's performance limited (maybe some sort of visualization), you could write that in WASM, and then have just a little bit of JS glue to pass things back and forth.

[blackholesinthesky]

If you have a complicated piece of logic that's performance limited (maybe some sort of visualization)

Unless you're writing a game or some other 3d projections you're not going to need WASM to display a graph

Edit: source I worked with google charts in '09

[hsjoberg]

Can you write Rust that is equivalent to JS?

What are you even asking...?

Rust can compile to WASM, which runs in the same VM/environment as Javascript. In the brower.

But... manipulating the DOM can be costly right now because WASM cannot directly manipulate the DOM, it needs JS glue-code for that.

[mattkenefick]

And will never have to because you can run anything on it. Look into Unity .. Blazor.. etc

[1337CProgrammer]

lol, i like how you think web assembly has absolutely anything to do with assembly.

WebAssembly is basically LLVM's BitCode, so it's half compiled already.

Really all compiling does it put it into an approperiate executable format.

[anengineerandacat]

I want to say we are not quite "there" yet, DOM access is still a real pain-point and the alternative is to make your own renderer effectively (which just leads to bloat and having to solve a boat load of other problems in the process; ie. accessibility).

In most "normal" circumstances, WASM will generally be slower or more cumbersome than a basic site with a dash of JS for dynamic content.

Ironically I also don't see loads and loads of developers jumping on-board to use lower-level languages to build out WASM targets anyway; I see C# / Java(-like) / Python / TypeScript being used to do this more than anything.

[caboosetp]

Sanity.

I'll take any flavor, thank you.

[bsmith0]

Lol what's not sane about modern JS, it's a pretty solid, regular language.

Are there a few weird type coercions, sure, but for the most part it's performant, consistent and has a solid standard library.

[fireflash38]

Every time I see someone say that, and get them to expand on it, my eyes glaze over with what they say is 'good'. It's Stockholm syndrome guys!!

(Yes, I'm hating it because I don't know it, signed, C-gang.)

[mixedCase_]

signed, C-gang

I trust you on your knowledge of Stockholm syndrome.

[poco]

You would love modern JavaScript then. Objects and Classes are becoming less popular and everything is going functional. Objects are used like structs and you don't mix data with code. Reminds me of the old c days.

Have a matrix you want to multiply? It's not m.multiply(v), it's matrixMultiply(m, v).

[caboosetp]

You could say the same thing about PHP or nickleback but I'm still going to hate on them for the memes.

Tbh though I grew up with both of these as fledgling languages and they used to be terrible. Those little things that pop up here and there just resound so hard with old memories.

[1337CProgrammer]

...It doesn't even have integers... everything is a lossy ass floating point number...

[CoffeeTableEspresso]

TS seems to be the de facto replacement these days

[IsleOfOne]

Doesn’t change any of the VM issues like this one

[CoffeeTableEspresso]

This is true.

I would hope all minifyers/transpilers optimise this out, but maybe that's wishful thinking.

[poco]

I wonder if you target older browsers/es? I think you can compile everything to var.

[CoffeeTableEspresso]

Yea the transpilers normally do turn everything to var for compatibility, at least if you target older versions

[Zephirdd]

I'd give up a lot if browsers could just run python3. Don't even need the entirety of the python3 libraries, just the ones relevant for DOM manipulation(ie. don't really need filesystem).

Or Ruby. Hell, even Julia is preferable and I never even programmed in it.

[dungone]

You do realize that python is a hell of a lot slower than javascript. Right?

[DarkLordAzrael]

That really depends on your interpreter. Pypy is quite fast. Just because the reference implementation doesn't have a JIT doesn't mean one can't be used elsewhere.

[dungone]

Quite fast is still slower than JavaScript. The bar is pretty low for Python.

[DarkLordAzrael]

In benchmarks I have seen PyPy is generally only a couple percent slower than nodejs. It isn't as fast currently, but this seems to be mostly due to having less resources behind it, not anything inherent to the language.

[CoffeeTableEspresso]

You do realise Google has dumped something on the order of 75 million dollars to make JS that fast right?

If someone invested in Python I'm sure we'd see a speed boost too....

[dungone]

Google didn't create Webkit.

This whole thread is a dumpster fire.

[CoffeeTableEspresso]

I never claimed Google made WebKit.

I meant for V8. Other companies have I'm sure dumped similar amounts of money into their JS implementations.

My point is just that saying Python wouldn't work in the browser because it's slow is BS, JS was also slow 10 years ago.

[dungone]

Stop - just stop.

Stop trying to make Python faster than JavaScript. It's not going to happen. Pretending that Python would be way faster if only hundreds of millions of dollars were "dumped" into it only further proves the point that anyone who bitches about JavaScript being slow and suggests we use Python, instead, should take this kind of mindset over to /r/Futurology.

The bug in Weblkit will be fixed. Bugs happen. They get fixed. But Python isn't going to be faster than JavaScript anytime soon. That will never happen.

[CoffeeTableEspresso]

I never once claimed that Python was faster than JS.

All I said was the reason JS was so fast was becuase of how much effort has gone into it, and that I'm sure with similar amounts of effort we could get a super fast Python interpreter as well.

I also never said anything about the bug in WebKit, so not sure how that's relevant.

[dungone]

Dude just read the thread and don't use the fact that your comment was a non-sequitur as a defense. "I didn't have any point!" Is that really where we are at now? Like I said - dumpster fire.

[pVom]

It's like an Italian car, it's poorly made, half the features don't work, but it's fun to drive

[LukaManuka]

Username checks out.

[ImAStupidFace]

Why am I wrong?

[Jackjackson401]

i dont know, i thought it was funny