[zelly]

The problem with Web Components is it's slower than React or other vDOM implementations. Also everything is a string. To re-render, you have to manipulate the innerHTML--usually replacing the string every update. To pass a prop to a component in a modular way, you have to pass a string attribute (e.g. something like <my-component my-attribute="[1,2,3]"/>). Even though v8 is extremely fast at string operations, it's just not a good practice and doesn't scale.

W3C standardized Web Components before React existed and took off, unfortunately. I expect the next standard to just be React itself (or a barebones version that the library can build on top of), patent licenses permitting. I'm pretty sure as a C++ precompile, it would be unstoppable and end the debate for good.

[semiquaver]

Every real world use of Web Components that I’ve seen uses <template> elements and/or imperative DOM methods to implement rerendering. These are blazing fast and exactly what React uses. It’s possible to build a slow app using Web Components, but that’s true of every library, including React.

[Izkata]

Same here; I suspect they've mixed up defining the component (where some examples do use innerHTML) and using the component (which don't).

[brundolf]

> Web Components is it's slower than React or other vDOM implementations

> To re-render, you have to manipulate the innerHTML--usually replacing the string every update

"Usually" is relative, I guess, but nothing's stopping you from using the imperative DOM APIs to update the component's contents; I daresay this would be the typical thing to do. These APIs will be just as performant as anything else out there. What you're really giving up, then, is the reactive programming model. Web Components are just a way of modularizing things; they have nothing to say about how you update the DOM (for better and worse).

You are right (I think) that there's no good way around converting attributes to and from strings, though the performance overhead there should be minuscule in most cases. The bigger problems with that are a) some data (like functions) can't be serialized at all, and b) it leaves a lot of room for passing invalid values

[megous]

You can use DOM node properties instead of attributes, when working with custom elements from JS. No seraialization/deserialization to/from string there.

[zelly]

If you're using a framework like lit-html as the author recommends, it will replace the string every update. Most people will prefer that way since it's more ergonomic and similar to React. You could do imperative DOM updates, but that'd be like going back in time to jQuery.

[claviska]

This is false. It does not replace the entire string, but uses a template literal to identify which changes need to be made before selectively updating the DOM.

This video is a few years old, but the core concepts remain the same.

https://m.youtube.com/watch?v=Io6JjgckHbg

[robertlagrant]

Wow, that's a pretty compelling video. I guess they all are, but I like the use of modern web standards.

[jaredcwhite]

This simply isn't true. Tagged template literals are not string concatenation. Also any "thin layer" of tooling on top of vanilla web components (like Lit) is entirely capable of passing complex objects as props. String-only "props" are only the case for literal HTML attributes in your source HTML—and even then you can embed JSON in an attribute and get a real parsed object within the component.

[dmitriid]

> Tagged template literals are not string concatenation

They are not concatenation by themselves. But for them to be useful, you will end up doing a lot of it because there's nothing else to do with strings than parse (often with regexps [1]) and concatenate [2] the strings. And then you dump the concatenated string into the DOM using `.innerHtml` [3]

There's no magic.

[1] https://github.com/lit/lit/blob/main/packages/lit-html/src/l...

[2] https://github.com/lit/lit/blob/main/packages/lit-html/src/l... and https://github.com/lit/lit/blob/main/packages/lit-html/src/l... and so on.

[3] https://github.com/lit/lit/blob/main/packages/lit-html/src/l...

[dtagames]

I use Lit every day and I have no idea what you're talking about.

Any property can be a full JS object. When the property is changed, it is re-rendered in your component. I have never touched innerHtml and my Lit apps pass and render all kinds of stuff into html`` tagged templates.

It's really pure magic because you can freely mix regular old HTML and regular attributes with dynamic data and data binding. There's more than one way to write anything which gives you great flexibility. I adore tagged templates, and they work for CSS and SVG, too.

[dmitriid]

> I use Lit every day and I have no idea what you're talking about.

I'm talking about how lit is implemented internally and that's why I provided links to relevant parts of lit's code.

People having no idea how things work is the bane of our industry. And that's why we have objectively false statements like "regular old HTML and regular attributes with dynamic data and data binding".

Lit is almost as far from "regular old HTML" as React's JSX is: lit is a HTML-like DSL that even has constraints on how you use tagged literals themselves.

E.g. `<${tagName}></${tagName}>` is a valid tagged literal and it's invalid in lit.[1]

> they work for CSS and SVG, too.

If lit lets you mix SVG with custom elements, they don't really use custom elements. See discussion https://twitter.com/Rich_Harris/status/1198339672361119745?s...

[1] https://lit.dev/docs/templates/expressions/#invalid-location...

[brundolf]

Right, all I'm saying is this is nothing intrinsic to the Web Components standard like the parent comment suggested. It's just one particular way you might use them.

[sibit]

> To pass a prop to a component in a modular way, you have to pass a string attribute

Is this actually how people pass props with Web Components? I've only used web components for a few years but I've always created a new instance of the class and I pass props using the constructor like:

`${new ExampleComponent(props)}`

Then in the constructor it's just this.state = {...this.state, ...props}

[mhoad]

I’m not sure what you’re referring to here honestly but React is substantially behind web components in terms of every performance metric I can think of.

Boot up, runtime, micro benchmarks and at scale.