[spankalee]

This is just a lie perpetuated by the React team 10 years ago

All HTML elements are JavaScript objects that have properties. You can pass arbitrary data to custom elements via those properties.

Look at any modern HTML template system and you'll see the ability to pass data to properties declaratively.

[MrJohz]

Well it's not a lie, it's how HTML and the DOM work. Attributes are strings, and what you write in HTML will be passed as attributes.

You do also have access to properties, but only in Javascript — you can't for example write something like `<my-custom-component date="new Date(2024, 02, 04)">`. That means that if you need to pass around complex data types, you need to either manipulate the DOM objects directly, or you need to include some sort of templating abstraction that will handle the property/attribute problem for you.

This is my main criticism of web components. At the simplest levels, they're not useful — you could build this website very easily without them, they aren't providing a particularly meaningful abstraction at this level of complexity. But at the more complex levels, they're not sufficient by themselves — there's no state management concept, there's no templating, there's not even much reactivity, other than the stuff you could do with native JS event emitters.

As far as I can tell, the best use-case for web components is microfrontends, which is a pretty useful use-case (much better than iframes), but it's very niche. Apart from that, I really don't see why you wouldn't just write normal Javascript without worrying about web components at all.

[spankalee]

It is absolutely a lie, because web components can handle arbitrary data just at much as any framework.

You're holding web components to a higher standard here in expecting them to take arbitrary data in HTML when HTML itself doesn't support arbitrary data. Notably you can't assign arbitrary data to framework components from within HTML either, so how are web components any more limited?

[MrJohz]

The original comment was that "all HTML attrs must have string keys and values", which is completely true.

The point of web components is that they create normal HTML elements. So it makes sense to consider what the value of them being normal HTML elements is. You can write them directly in your HTML source code, for example. But if you do that, you only get access to attributes and not to properties, and therefore everything needs to be strings. Alternatively, you can treat them as DOM nodes in Javascript, at which point you get access to properties and can use non-string values, but now you've got to deal with the DOM API, which is verbose and imperative, and makes declarative templating difficult.

Yes, we could compare them to components from other frameworks, but that's honestly an absurd comparison. They're simply trying to do different things. Frameworks aren't trying to create HTML elements. They're trying to reactively template the DOM. It's just a completely different goal altogether. The comparison doesn't make sense.