So for example in case of parsed templates, to pass a callback to onClick you'd need to define a convention on how you're going to locate the callback by a given string (since you can't pass the function itself, you need to pass some "name" of that function). Whatever logic that will be, the result will not feel like React anymore because you're back to typical framework-specific template magic instead of using plain JS.
Putting behaviour in HTML is a bad idea. Leave it in JS, and have one place to go when the behaviour changes.
This is not what I'm doing. JSX is JS. I'm not putting any logic "in HTML". If I were able to express what I'm doing in mustache-style syntax, it would be:
Blah blah <a onclick="{{ callback }}">Click me</a> Blah
What's your ideal way of registering an onclick callback?
* With React & ESLint you get basic checks to make sure you're not passing non-existent variables
* Your IDE understands what you're doing and lets you jump to callback definitions
* You understand what you're doing because you have one obvious place where you do templating and data binding.
* Your actual behaviour logic is still separated from your template, living in some other JS file.
On the other hand, if you add event listeners to HTML from JS the classic way, you get other problems:
* You're querying the DOM tree by CSS classes or some custom attributes. It's surely a familiar way of doing things, but also fragile and unintuitive.
* It requires your JS to know the structure of your DOM to some extent, and that structure is defined elsewhere. So it's basically the same problem as with mustache templates – passing around magic strings – but the other way around.
* Neither ESLint nor IDE will help you do it.
Edit response to person below (rate limit): there's no 'problem', just that mustache is still more familiar. Moving JSX into a different file doesn't change that.