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by twhb 3227 days ago
I think you misunderstand. The names are unrelated to React as well, they are native. Defined by the same standards bodies that define JavaScript itself, implemented by the browsers themselves. On a blank HTML page that includes neither React nor anything else, the line `document.body.className = "foo";` sets the body's class to "foo". (And `document.body.class = "foo";` does not.)

All JSX is doing is transforming `<div className="foo">` into `[create div element]; div.className = "foo";`. If you wrote `<div class="foo">`, JSX would faithfully transform it into `[create div element]; div.class = "foo";` - which doesn't work.
3 comments
allover 3227 days ago
Whilst you're correct, that's where the names are from, it's also not totally accurate to suggest it has nothing to do with React.

React defines `React.createElement`, `<div class="foo"/>` transforms to `React.createElement("div", { "class": "foo" })`, so React could convert that under the hood to set className correctly.

Preact does something similar to allow this. However it now seems it is now too late for React for too little benefit. And there's a downside [1]:

> The JSX transform used to do that, but we don't recommend it because it's confusing if you ever try to pass class= or for= as a prop to your own components – you wouldn't expect to access them with a different name.

[1] https://github.com/facebook/react/issues/4433#issuecomment-1...

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tshaddox 3227 days ago
Good point. I didn't realize that the native DOM properties are also called "className" and "htmlFor". My point still applies though, that this isn't a JSX syntax issue, your point is that it's also not even a JSX-specific semantics issue.
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tripzilch 3227 days ago
not quite, the list of reserved keywords was made up by the committee that designed the first version of ecmascript in 10 days (or however the exact story goes).

many years later, the workarounds like class -> className were designed by whatever party exerted most control over the JS DOM API (which is not really part of "Javascript itself") at the time, and who also brought you inconsistent camelcasing such as "onclick" ...

it's neither quite "native", nor is "defined by the same standards bodies" much of a sign of good design or worthy of copying.

feels more like if someone were to build, say, a modern high perf numerical library that includes necessary workarounds tributed to the eax/ax/ah/al peculiarities of x86 assembly.

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