12 ms·

I think you are being a bit overdramatic about JSX. There was zero learning curve -- except for a few errors initially when using class instead of className...

by j_r_f 10y ago

I think you are being a bit overdramatic about JSX. There was zero learning curve -- except for a few errors initially when using class instead of className... The argument that DOM.div() is more readable than <div/> is honestly hilarious to me. Any non-trivial tag structure will be unnecessarily complicated through the API. Especially when you can just write it almost exactly how it's going to look when it becomes HTML in JSX.

lhorie 10y ago
DOM.div() vs <div/> seems like a bad example. IMHO, when you get an element with tons of event handlers and conditional classes, or when you have a deep chain of ternaries that's where angled bracket syntax starts to become unwieldy. The className thing is a big deal too, in my opinion. Preact and Mithril do what you would expect, and perf doesn't suffer, so why can't React/JSX normalize it as well?
- Bahamut 10y ago
  className was named that to avoid conflict with the JS class syntax originally I believe, since JSX is inline - they probably could put in the work to change it at this point, but it seems like a minimally beneficial change but massively disruptive at this point.
  - jmtulloss 10y ago
    It was named that to match the DOM api[0], which React does whenever possible. The DOM api is probably named for the reason you state. [0]: https://developer.mozilla.org/en-US/docs/Web/API/Element/className https://developer.mozilla.org/en-US/docs/Web/API/Element/cla...
    - rmetzler 10y ago
      And the reason why the DOM API uses className is: class is a reserved keyword in JavaScript for a long time.
  - lhorie 10y ago
    There's also stuff like onClick, readOnly, xlinkHref... I would guess that a healthy number of React-related google searches are related to these gotchas
- debaserab2 10y ago
  If you have deep chains of ternarys, that's a symptom that you should be splitting your rendering code into another function or component. This would be true regardless or what approach you are taking to templatihg. That's one thing I really appreciate about jsx: the lack of rich template code syntax makes it glaringly obvious when your template code is doing too much and should be refactored. It does a really good job of keeping your logic in javascript and out of your template.
  - lhorie 10y ago
    Refactoring into functions/components doesn't magically make a complex ternary tree go away. It helps the body of each branch be less noisy but the ternary tree will still be there. You're talking about taking something like `foo && bar || baz && quux` and turning it into `isSomeCondition()`, but that's a pretty obvious refactor in any templating system. I'm talking about things like return ( <div>{ x.type === 'foo' ? <Something/> : x.type === 'bar' ? ( <div> <h2>More stuff</h2> <Another data={x.data}/> </div> ) : x.type === 'baz' ? <Another data="baz"/> : null }</div> ) At this point, I think it's perfectly valid to have the opinion that JSX isn't helping much, since the JS-to-HTML ratio in this case is relatively high. Refactoring would just make it more difficult to mentally piece things back together given you would end up with sparse component instantiations scattered amidst otherwise-procedural js code, as opposed to the more ideal single-root, declarative virtual dom tree.
    - debaserab2 10y ago
      Without understanding what x.type is, I'd be inclined to write that without any ternary operator at all using plain old if statements with each returning JSX markup. I try to keep logic in JSX to simple ternary operators and loops at most. JSX is really just shorthand for DOM.div() for me. I imagine the code structure looks pretty similar to actually using DOM.div though. I'm not seeing how programmatically creating markup with DOM.div results in significantly different code, although if you have some good examples I'd love to understand them better.
- nkohari 10y ago
  Ternary operators should never be nested, whether you're using JSX or not. If you have that many conditionals you should use variables and/or decompose the optional pieces into sub-components. Pretty much any time you have a tag that has a huge number of attributes, it's a smell that you need to decompose something. Variable assignment is the simplest answer, which takes advantage of the fact that null or undefined values are ignored in JSX: const Dashboard = (props) => { let avatar; if (props.user) avatar = <Avatar user={props.user} />; return ( <div> {avatar} ...some other content... </div> ); }; Regarding class vs. className: class is a reserved word in JS. It's not really a perf thing, it's the fact that JSX was intended as a very simple transform. If JSX used class instead of className, the transpiler would need to be contextual since "class" would sometimes mean "css class" and sometimes "JavaScript class". The baseline complexity for the parser would be higher and could lead to all sorts of complexity. Rather than deal with that the React team avoided the problem by using className instead, keeping things simple.
  - duncanawoods 10y ago
    I think this proves lhorie's point. Markup syntax is dominated by code when you are building complex dynamic apps instead of static documents. What do you really gain by putting angle brackets around Avatar instead of calling a function? FWIW I believe new react devs are slow to realise they can use local variables like this because JSX looks like it is doing string templating instead of object instantiation.
    - nkohari 10y ago
      The example I gave was simplistic, but the value of JSX is the ability to easily nest elements. For instance, let's take my previous example and say we're creating a profile link: const Dashboard = (props) => { const {user} = props; let link; if (user) { link = ( <a href="..."> <Avatar user={user} /> <span>{user.name}</span> </a> ); } return ( <div> {link} ...some other content... </div> ); }; If you want, you could create a `createProfileLink()` function, or you could create a `ProfileLink` component, or you could keep it as a variable in the `render()` function. This flexibility is what makes JSX powerful.

by j_r_f 10y ago

lhorie 10y ago

DOM.div() vs <div/> seems like a bad example. IMHO, when you get an element with tons of event handlers and conditional classes, or when you have a deep chain of ternaries that's where angled bracket syntax starts to become unwieldy. The className thing is a big deal too, in my opinion. Preact and Mithril do what you would expect, and perf doesn't suffer, so why can't React/JSX normalize it as well?

Bahamut 10y ago
className was named that to avoid conflict with the JS class syntax originally I believe, since JSX is inline - they probably could put in the work to change it at this point, but it seems like a minimally beneficial change but massively disruptive at this point.
- jmtulloss 10y ago
  It was named that to match the DOM api[0], which React does whenever possible. The DOM api is probably named for the reason you state. [0]: https://developer.mozilla.org/en-US/docs/Web/API/Element/className https://developer.mozilla.org/en-US/docs/Web/API/Element/cla...
  - rmetzler 10y ago
    And the reason why the DOM API uses className is: class is a reserved keyword in JavaScript for a long time.
- lhorie 10y ago
  There's also stuff like onClick, readOnly, xlinkHref... I would guess that a healthy number of React-related google searches are related to these gotchas
debaserab2 10y ago
If you have deep chains of ternarys, that's a symptom that you should be splitting your rendering code into another function or component. This would be true regardless or what approach you are taking to templatihg. That's one thing I really appreciate about jsx: the lack of rich template code syntax makes it glaringly obvious when your template code is doing too much and should be refactored. It does a really good job of keeping your logic in javascript and out of your template.
- lhorie 10y ago
  Refactoring into functions/components doesn't magically make a complex ternary tree go away. It helps the body of each branch be less noisy but the ternary tree will still be there. You're talking about taking something like `foo && bar || baz && quux` and turning it into `isSomeCondition()`, but that's a pretty obvious refactor in any templating system. I'm talking about things like return ( <div>{ x.type === 'foo' ? <Something/> : x.type === 'bar' ? ( <div> <h2>More stuff</h2> <Another data={x.data}/> </div> ) : x.type === 'baz' ? <Another data="baz"/> : null }</div> ) At this point, I think it's perfectly valid to have the opinion that JSX isn't helping much, since the JS-to-HTML ratio in this case is relatively high. Refactoring would just make it more difficult to mentally piece things back together given you would end up with sparse component instantiations scattered amidst otherwise-procedural js code, as opposed to the more ideal single-root, declarative virtual dom tree.
  - debaserab2 10y ago
    Without understanding what x.type is, I'd be inclined to write that without any ternary operator at all using plain old if statements with each returning JSX markup. I try to keep logic in JSX to simple ternary operators and loops at most. JSX is really just shorthand for DOM.div() for me. I imagine the code structure looks pretty similar to actually using DOM.div though. I'm not seeing how programmatically creating markup with DOM.div results in significantly different code, although if you have some good examples I'd love to understand them better.
nkohari 10y ago
Ternary operators should never be nested, whether you're using JSX or not. If you have that many conditionals you should use variables and/or decompose the optional pieces into sub-components. Pretty much any time you have a tag that has a huge number of attributes, it's a smell that you need to decompose something. Variable assignment is the simplest answer, which takes advantage of the fact that null or undefined values are ignored in JSX: const Dashboard = (props) => { let avatar; if (props.user) avatar = <Avatar user={props.user} />; return ( <div> {avatar} ...some other content... </div> ); }; Regarding class vs. className: class is a reserved word in JS. It's not really a perf thing, it's the fact that JSX was intended as a very simple transform. If JSX used class instead of className, the transpiler would need to be contextual since "class" would sometimes mean "css class" and sometimes "JavaScript class". The baseline complexity for the parser would be higher and could lead to all sorts of complexity. Rather than deal with that the React team avoided the problem by using className instead, keeping things simple.
- duncanawoods 10y ago
  I think this proves lhorie's point. Markup syntax is dominated by code when you are building complex dynamic apps instead of static documents. What do you really gain by putting angle brackets around Avatar instead of calling a function? FWIW I believe new react devs are slow to realise they can use local variables like this because JSX looks like it is doing string templating instead of object instantiation.
  - nkohari 10y ago
    The example I gave was simplistic, but the value of JSX is the ability to easily nest elements. For instance, let's take my previous example and say we're creating a profile link: const Dashboard = (props) => { const {user} = props; let link; if (user) { link = ( <a href="..."> <Avatar user={user} /> <span>{user.name}</span> </a> ); } return ( <div> {link} ...some other content... </div> ); }; If you want, you could create a `createProfileLink()` function, or you could create a `ProfileLink` component, or you could keep it as a variable in the `render()` function. This flexibility is what makes JSX powerful.