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by kamilafsar 1473 days ago

People like to hate everything related to JS these days. But when I see libs like these I'm just very grateful for the person(s) who invented JSX [1]. And evenly for MSFT implementing it into TS as a first-class citizen. It's just so much more readable.

Scala is the only other language I know of which has some kind of XML/HTML syntax support (scala.xml). (But it looks like it got removed. [2])

[1] https://reactjs.org/docs/introducing-jsx.html

[2] https://github.com/scala/scala-xml

11 comments

the_gipsy 1473 days ago

I don't think JSX is very readable. If you squint it may look like HTML, but when you try to actually read it, it's all off. Different attributes, bizarre templating, blurred line between rendering and code. The latter in practice is always a complex mix of view/state/ callbacks with react.

lucideer 1473 days ago

You're confusing JSX and the React target for JSX; only the latter has the problems you mention.

This is a very common confusion because most people approach JSX via React, and as such never really grasp that JSX is a separate, independent thing. If you're interested in learning it standalone, I'd highly recommend working with either the Typescript `jsxFactory` compiler option, or the `@babel/plugin-transform-react-jsx`

jraph 1473 days ago

Isn't JSX essentially syntax sugar for function calls (to a specific "create element" function), and therefore bound to code/rendering mix regardless of React? I see JSX syntax as fancy JS expressions. It seems like everything the parent said could apply to any use of JSX, except for the attribute naming issue.

The "opposite" approach being using a template language like the one in Svelte or Angular… or like PHP (or Velocity, or Jinja) (for me JSX is not a template syntax at all).

I think template languages are also prone to rendering / logic mix, I don't know what is an elegant solution to this problem apart from getting used to this reality. Maybe something like QML, using data models, instead of having a for loop to render lists for instance.

lucideer 1473 days ago

> Isn't JSX essentially syntax sugar for function calls

Yes. Which makes any issues the gp mentioned entirely up to the implementation of that function call.

> seems like everything the parent said could apply to any use of JSX, except for the attribute naming issue

If by "could apply", you mean anyone could write a function that has those issues, then yes I guess. My point was that if you want to avoid those, they're in no way inherent to JSX. Is that what you meant?

I mean, I guess "blurred line between rendering and code" is less about the function implementation, and more about project / file organisation choices (including conventions of a frontend view framework community), but it's still certainly not inherent.

> I think template languages are also prone to rendering / logic mix

True. I think you do need a lot of discipline if you want to keep a clear and consistent separation, and it's also not always worthwhile (there's a codebase-approachability trade-off with abstraction & locality of context).

For arguments' sake though here is a quick-and-horribly-dirty example of JSX syntax separation (not recommended but demonstrative): https://codepen.io/lucideer/pen/jOZvwVz?editors=0010

jraph 1473 days ago

I think I don't agree: I think the possibility of mixing rendering and logic is inherent to JSX. While users of the syntax can probably (deliberately) avoid mixing rendering and logic too much, there's no implementation of JSX that can prevent its users from mixing the logic and the rendering if they want to do so: it will always be possible for a user to mix the JSX tags with arbitrary Javascript because the full JS language is available in JSX tags and JSX tags can be used in Javascript code.

In contrast with HTML, where there is no way one can mix the logic and the UI because it is syntactically impossible. You have to get the DOM element from a script and to fill it data (well, actually, you can with the script tag and on* attributes, but let's consider HTML without them, only allowing script tags in <head> for instance so our restricted version of HTML remains useful).

I think you need the rendering to be data, not code, to "forbid" this mix (and soon enough, you reinvent some kind of lisp I guess)

lucideer 1473 days ago

> there's no implementation of JSX that can prevent its users from mixing the logic and the rendering if they want to do so: it will always be possible for a user to mix the JSX tags with arbitrary Javascript because the full JS language is available in JSX tags and JSX tags can be used in Javascript code.

That's fair. If that's what you're looking for, then JSX is not the answer. I don't think we disagree though - I was merely pointing out separation is possible (even if not strictly enforced).

Personally, I am a fan of the component-driven model (criticised above for "blurring the lines"). As I mentioned, it's a trade-off, and I think any potential "blurriness" is far outweighed by the context and reduced abstraction wins from a code-readability & codebase approachability perspective. Heavily separated templating efforts often leads to codebases with deeply nested hierarchies for views -vs- controller logic that require having 4+ split pane editors open just to understand extremely local snippets of data flow. This is particularly egregious when e.g. trying to audit codebases for injection mitigation.

icambron 1473 days ago

I guess I’m not sure what you want though. If you want to render things dynamically, that dynamism has to live somewhere. And wherever that is, it’s possible to abuse. For example, what does “fill in the data” really mean? For a non-trivial app it has to mean the ability to generate fresh markup from your data, and that process can mix concerns.

deepstack 1473 days ago

Hmm, I think a long time ago (around 2005 or 2006) JSX was briefly considered to be party of ES standard. It didn't make it, and shortly after FB introduced React.

Think it may have being easier if JSX is just included in ES as a standard. So yes and no, JSX introduced by FB via react is a just a syntax sugar, however the original JSX is a meant to be a ES standard, with each node as a tree structure.

https://www.ecma-international.org/publications-and-standard...

lucideer 1473 days ago

You're describing E4X. E4X and JSX are both XML-inspired syntaxes, but beyond that have relatively little in common in how they function.

E4X was supported by Firefox for a while, but I think support was removed.

jraph 1473 days ago

The way I see it, syntax sugar can be part of the language proper.

For instance classes in JS are sugar syntax to define a function that defines fields in this and prototype members of this function.

Arrow functions are sugar syntax to define functions bound to a specific this.

async / await is sugar syntax for promises.

for..of is sugar syntax for iterating over an iterable.

the_gipsy 1472 days ago

No, I am not confusing them. My comment is about JSX' awkward attribute (re-)names, only expressions in brackets but full function calls in loops (map). It's horrible.

lucideer 1472 days ago

> JSX' awkward attribute (re-)names

The attribute renaming is a React feature. JSX doesn't rename attributes. See here for example https://codepen.io/lucideer/pen/jOZvwVz?editors=0010

> only expressions in brackets but full function calls in loops (map)

Not sure what you mean here. Function calls are expressions - they work bare in brackets & also as method args (like the arg passed to the map method on an array prototype, which is called while "loop"-ing that array). This is all Javascript functionality, not really specific to JSX in any way?

the_gipsy 1472 days ago

I stand corrected about JSX attribute renaming! However I still see it being applied in practice for 99% of JSX use cases.

The problem with "only expressions in brackets" is that then you can write code in the template, but it's massively different to regular code. Worst of both worlds: code in templates and weird subset of code.

lucideer 1472 days ago

> you can write code in the template

If this is undesirable as a feature, then yes, JSX is not an appropriate choice. JSX is the furthest thing from logic-less templating. But that's a deliberate design decision.

> it's massively different to regular code

It's not. It's just regular code - there are no differences.

> weird subset of code

It's not weird. It's any JS expression. All JSX brackets are values, and JS statements don't have return values, so embedding a JS statement within a JSX value would serve no purpose. What would it do?

All statements in JS can be expressed as expressions directly (ternary/array methods) or indirectly (nested within a function expression), so there's no loss of functionality - it's not even really a subset in that sense.

nikonikoniko 1473 days ago

I find that very interesting, I have the opposite reaction to JSX. Not wanting to use it has been one of the biggest reasons I have moved into using ClojureScript/Hiccup for front-end applications.

I find JSX extremely hard to read and work with and reason about.

capableweb 1473 days ago

After you get a taste of the free world of hiccup/reagent where it's just vectors and maps to create HTML, its really hard to imagine going back to anything else. Being able to use the same programming language in your "HTML template" (which are just core data structures in a specific shape) as for the rest of your programming is just icing on the top.

Small example for people to understand the difference:

    // HTML & JSX
    <div id="person">
      <h1>Niko</h1>
    </div>
    
    // Hiccup
    [:div#person
      [:h1 "Niko"]]

dgb23 1473 days ago

I think the big differences don’t come out visually.

In JSX you might be struggling with expressing certain things, because JS has a statement expression syntax. So you have to circumvent that. In Clojure everything is an expression already.

In JSX you can manipulate components with HoCs. In Clojure it’s just data, no special ceremony needed.

On the client, if you’re using React, you might use hooks to keep travk of state, which are a special construct that don’t exist in JS. In Clojure, if you use something like reagent, you just use atoms, they have a special purpose implementation, but they look and feel like regular old atoms.

However I have to say, JSX and React are very productive even with those limitations, simply because the tooling around it is so good.

nicoburns 1473 days ago

Hopefully the limitations around expressions in JS will go away at some point and JS will become properly expression orientated. There are already proposals for this, although they currently seem to be stalled.

mic47 1473 days ago

IIRC php/hack had it before jsx existed:

https://docs.hhvm.com/hack/XHP/introduction

https://github.com/phplang/xhp

capableweb 1473 days ago

That's actually the heritage of JSX!

XHP was launched in 2010 (https://www.facebook.com/notes/10158791323777200/)

The first version of FaxJs (the precursor to React) was launched in 2011, being directly inspired from XHP (https://github.com/jordwalke/FaxJs)

React was made in 2012 by the same person who made FaxJs, taking the best ideas from FaxJs and creating React.

So yeah, JSX actually comes from the idea of XHP :)

amenghra 1473 days ago

https://github.com/facebookarchive/xhp-php5-extension if you are interested in seeing how Marcel initially implemented XHP for PHP.

The concept was popular at Facebook, so it made its way into HPHP, HHVM, and later ReactJS.

cies 1473 days ago

To me JSX is the opposite of what Maud (Kotlinx.html, Elm's HTML lib, Haskell's type-of-html) does. In Maud you write "just code", and "as code". In traditional template engines you have a big string with holes, if-elses and loops. In JSX you write templates as if it is a traditional templating engine, but under the hood it gets translated to JS-code.

Somehow JSX seems to be "worst of both worlds" to me.

Some of these HTML-templates-as-code libs (like Kotlinx.html) are generated from a formal HTML specification. This is really nice, and makes it more type safe (only allow tag nesting that is allowed, and only allow attributes that are allowed; ofcourse with escape hatches).

ptrik 1473 days ago

Related library in Rust: https://docs.rs/typed-html/latest/typed_html/

ghusbands 1472 days ago

JSX has some questionable design limitations in it, though. Like, these work as expected:

  \<h1>Hello, world!\</h1>
  \<img alt="Hello, world!"/>
  \<h1>Hello, {place}!\</h1>
  \<img alt={message}/>

But this doesn't:

  \<img alt="Hello, {place}!"/>

And as other commenters note, it's designed around React internals, meaning you get rules around capitalisation that wouldn't otherwise exist. And so on.

centixel 1472 days ago

I tend to solve that problem with either:

  <img alt={"Hello, " + place}/>

Or, for more complex interpolation:

  <img alt={`Hello, ${place}`}/>

jen20 1473 days ago

> Scala is the only other language I know of which has some kind of XML/HTML syntax support

Visual Basic .NET has XML literal support [1].

[1]: https://docs.microsoft.com/en-us/dotnet/visual-basic/program...

db48x 1473 days ago

I was there when E4X was introduced, about 20 years ago. It lasted about 5 whole years before people started to think it was old and crufty.

https://developer.mozilla.org/en-US/docs/Mozilla/Firefox/Rel...

ghusbands 1472 days ago

E4X couldn't really be used - it was never available enough (just one major browser) and there was no polyfill or to-JS compiler (those things weren't common at that time).

Had E4X been more widely released, I might have used it, as might many others. In retrospect, though, it's probably good that it didn't catch on, as it introduced a lot of extra syntax and operators, like a.@b, a.@*, a.*, a.b::c, a..b, a.(@b==x) and had semantics that affected large parts of the JS Runtime (how the delete operator works, how calling works, what += means, and so on).

db48x 1472 days ago

Some of those operators would have been pretty useful, though the ones for dealing with xml namespaces wouldn’t be.

Existenceblinks 1473 days ago

I don't hate js, I hate bloat, unnecessary dependencies, and unnecessary build tools. All I want to do to be able to use a html view lib is `import`.

pid-1 1473 days ago

HTML Jinja templates are supported in many editors. Jinja + plain Python is my favorite way of building static web pages.

baby 1472 days ago

I never liked JSX and have avoided it. Maybe I’m missing something.