The time is right for a DOM templating API

> Hard not to laugh out loud at "We know what good syntax for templating looks like."

First of all, it's not very nice to laugh in the face of someone advocating for progress on the web platform, which benefits everyone.

Second of all, yes we do now know what good syntax for templating is, it's basically jsx (and I'm saying this as someone who's really not a fan of React). It took the whole web by storm, it's been adapted for all kinds of frameworks, and it's undeniable that all js templating systems converged towards common attributes: templates-as-expressions, composition via nesting and control flow with just javascript (instead of specific template syntax).

I'm laughing because it just hits so hard. Started playing some role playing with friends again recently and we were looking for a template for the character sheets. You know what they have? A PDF. That is their template. Why? Because they design things that way.

And it is funny, because I can already feel the ideas that would go into templating this symbolically. Characters have 6 and 20 numeric attributes. But, I can already guess most would consider it a fault to manually place either of those on the page. Yes, the sheet has a limitation on how big your name can be. No, you can't really avoid that.

JSX is what happens when you no longer have a design and a dev team. It is great at that, even. But if you have a workflow where a designer makes a template and sends it over to a dev, it no longer really helps. You are much better off making something that can pick at artifacts that are handed off.

Instead, we seem to be aiming for an idea that will have to replace learning of everyone involved.

It's good when someone advocates for what they believe to be progress on the web platform, but it's not necessarily clear that this would be progress. And that line in particularly is amusing because we absolutely don't know what good syntax for templating looks like — that's why there's so many different options.

JSX is certainly the most popular because it's used in the most popular framework, but it has some very clear weaknesses. In particular, it has very clear semantics for a React-like, VDOM-based framework, but those semantics do not work as well for other kinds of framework.

For example, you mention control flow via ternaries/`.map`. This works great in React, where the entire template will be reevaluated every time any input changes. However, frameworks like SolidJS or Vue in Vapor mode work very differently, and typically evaluate JSX only once at component mount (or at least, as seldom as possible). To support these, these frameworks need to use either special components like `For`/`Show`, or directives like `v-if`.

There's also the issue of how to evaluate JSX. In theory, JSX is flexible, in that `<Cpt prop={expr} />` can be converted to any call of the form `h(Cpt, {prop: expr})`. Again, that's not true for SolidJS or Vapor mode Vue — in both of these frameworks, `expr` cannot be eagerly evaluated, so the traditional transforms just don't work. Both of these frameworks therefore have to include their own custom plugins for handling JSX correctly.

The author's suggestion to also use signals as a state mechanism suggests they're imagining something more along the lines of SolidJS. That's an odd choice (it's my personal go-to framework, but it's also very niche), but it also implies, as discussed, that JSX-in-the-browser wouldn't behave like JSX-in-React. From experience, that will cause problems! I've worked with React developers before who've really struggled to use SolidJS because of precisely this issue.

I don't think you understand what "template" means here, this has absolutely nothing to do with design or end result on the page. At no point would a designer be involved with templating the DOM.

It's in contrast to the imperative `document.createElement(...)` & `parent.appendChild(...)` APIs which you otherwise use in vanilla JS.

> yes we do now know what good syntax for templating is, it's basically jsx (and I'm saying this as someone who's really not a fan of React). It took the whole web by storm, it's been adapted for all kinds of frameworks, and it's undeniable that all js templating systems converged towards common attributes: templates-as-expressions, composition via nesting and control flow with just javascript (instead of specific template syntax).

This is not true. For instance:

Vue uses markup-based templates like this:

    <ul>
        <li v-for="item in items">
            {{ item.message }}
        </li>
    </ul>

Svelte uses text-based templates like this:

    <ul>
        {#each items as item}
            <li>{item.message}</li>
        {/each}
    </ul>

Angular uses markup-based templates like this:

    <ul>
        <li *ngFor="let item of items">
            {{ item.message }}
        </li>
    </ul>

And let’s not forget that the world doesn’t begin and end with JavaScript. Most other templating systems are either markup-based or text-based. For instance, Jinja2 is text-based:

    <ul>
        {% for item in items %}
            <li>{{ item.message }}</li>
        {% endfor %}
    </ul>

JSX really isn’t that great. Sometimes it feels like most React devs don’t know how to write a for loop or if statement because they mostly use map(), ternaries, and short-circuiting, which are not very ergonomic compared with markup-based approaches.

I confess your comment leaves me even more confused, all told. :D

I largely get the intent of what you are saying. But the entire point of why developers use templates is so that they can create pages that meet a design. And the entire reason I think they constantly get redone, is that design is inherently a visual process.

This is like trying to use formatting strings to try and handle localization. It just doesn't work. Folks will try and piecemeal all of the different strings in their application, only to find that some languages don't decompose the sentences in the same way. It can work wonders in small demos. It falls on its face when doing large things.

Don't get me wrong, I'm largely sympathetic to the gripes about the `createElement` and related methods. I've hacked on top of them many times with stuff similar to https://taeric.github.io/cube-permutations-1.html. They aren't pretty. But I'm not entirely clear on why template strings would be largely better?

Further, I could be surprised and this new API will usher in a better way of doing things. I'm not opposed to the effort. I just have a low prior on it succeeding. And I heavily disagree that we know what a good templating syntax is. Quite the contrary, until we learn to embrace visual artifacts, I do not think we will solve the templating needs.

> JSX really isn’t that great. Sometimes it feels like most React devs don’t know how to write a for loop or if statement because they mostly use map(), ternaries, and short-circuiting, which are not very ergonomic compared with markup-based approaches.

I'm the last person to vouch for React and the horrors it has inflicted upon web development, but the one thing it definitely got right compared to Angular (and Vue) is the use of JS for control flow, rather than fake attributes and whole new language.

JSX is as much a new language as Vue’s templating. JSX extends JavaScript syntax; Vue extends HTML syntax.

If you’re working on generating markup, it makes more sense to do that at the markup level than constantly switch between markup and imperative JavaScript.

It might use JavaScript for control flow, but does it really count when it uses it in a way that is not idiomatic at all? It’s not idiomatic JavaScript to use map instead of for everywhere, and it’s not idiomatic JavaScript to use ternaries instead of if everywhere. Writing JSX looks very different to writing normal JavaScript.

The difference is that JSX is using control flow from an actual programming language, whereas Vue is shoehorning control flow into declarative markup. This is the single reason React won the frontend framework market: they got the templating right.

PS: in modern JavaScript, using map rather than for loops is more idiomatic!

> This is the single reason React won the frontend framework market

Don’t be silly, the front-end landscape is a lot richer than you make it out to be. React hasn’t “won”, the last time there was a clear winner in front-end, it was jQuery.

> PS: in modern JavaScript, using map rather than for loops is more idiomatic!

No, it’s not, and this is exactly what I was talking about. for loops and map() serve distinct purposes.

for iterates through a series of elements.

map() transforms a series of elements.

It’s possible to use them both for the same things, but there is a very clear semantic difference between them. One doesn’t replace the other, they mean different things.

In the context of “I have a bunch of elements I want to iterate over and output”, what you want is a for loop. The reason why React devs have been convinced map() replaces for loops is that React has to force you into making everything an expression, so instead of writing for when it’s appropriate and map() when it’s appropriate, they have to write map() everywhere.

It’s good you ended on the one thing JSX got right: everything is an expression. It’s that simple. There’s nothing imperative about evaluating a template, it’s entirely covered by functional programming techniques. You’re just producing a value.

And yes, modern JavaScript uses tons of concept from functional programming, where it is understood that mutating values and triggering side effects should be a last resort. This is why a good js programmer uses ten times more maps then he uses for loops.

Maybe you don’t know how dominant React is today? Two third of JavaScript developers use React at work (https://2024.stateofjs.com/en-US/libraries/front-end-framewo...).

It feels like you’re out of touch, have you used JavaScript lately?

> mutating values and triggering side effects should be a last resort.

Output is a side-effect.

> This is why a good js programmer uses ten times more maps then he uses for loops.

This is a) massively overstating things, and b) not relevant to a case where zero for loops can be used.

> Maybe you don’t know how dominant React is today? Two third of JavaScript developers use React at work

I checked those figures before I posted that comment to double-check my memory. Two thirds is not anywhere close to “React won the market”. Android has ~72% global market share, but I’m sure you wouldn’t say that Android has won the smartphone market.

> It feels like you’re out of touch, have you used JavaScript lately?

We disagree, that doesn’t mean I’m out of touch. Try not to be so insulting.

It’s not an insult, if you think for loops are commonplace in modern JavaScript and React isn’t the dominant frontend framework by far (twice more used than the next in line, vue), you’re out of touch, it’s just a statement.

How can you not realize that producing a string or a tree of elements is a purely functional operation? There’s no side effect here. Are you familiar with the concepts of functional programming?

You are being insulting because every time we disagree, you ignore half of what I am saying to assume I don’t know what I am talking about. Two informed people can disagree but you don’t seem to get that. A conversation is not a competition where one person gets to prove the other person is ignorant.

Take “React winning”. We disagree that React won because I don’t think 66% of a market is “won”. But you jumped to the conclusion that I just didn’t know what I was talking about. Then I clarified that the difference in our opinion is not the knowledge of the market share but our judgment of it, and I gave the example of Android not having “won” the smartphone market with ~72% of the market… and you just ignored that and doubled down on calling me out of touch.

Take the use of map(). I am very clearly distinguishing between common usage and defined semantics. The gap between the two was what I was complaining about. But you ignored what I was saying and decided that I don’t know map() is used a lot in modern JavaScript, when that was the core of my complaint!

And for functional programming techniques, we disagree in how we think about the operation. You see it as data processing, I see it as I/O. I very specifically pointed out that I/O is a side-effect. This is a mainstream viewpoint in functional programming. But you ignored what we actually disagree about and assumed it’s just because I don’t know anything about functional programming.

Your approach to disagreeing with me is to ignore half the things I say so that you can attack me for being clueless. You need to do better.

I still think you’re misunderstanding what React is optimizing for. When you say "React has to force you into making everything an expression", you’re describing its core philosophy, not a constraint. JSX is built around the idea that rendering is just data transformation. It's UI as a function of state. That’s why using map() is idiomatic here. You’re building trees, not iterating imperatively.

Also, it bears repeating that React isn’t just slightly dominant. 82% of JS developers have used it according to the 2024 State of JS survey, and for good reason. It shaped the modern frontend mindset in a way that Vue or Angular haven’t, despite their own merits. For instance, many frameworks came up with their own version of hooks. It's telling that most new frontend frameworks are aiming for the "better React" position.

I realize we just have different interpretations of what "winning" means in a fragmented ecosystem, but it’s worth acknowledging how much React has set the tone for modern web development. UI as a function of state (and using map() a lot...) is here to stay.

> And for functional programming techniques, we disagree in how we think about the operation. You see it as data processing, I see it as I/O. I very specifically pointed out that I/O is a side-effect. This is a mainstream viewpoint in functional programming. But you ignored what we actually disagree about and assumed it’s just because I don’t know anything about functional programming.

I think you're wrong here. The point at which the rendered template is actually stuffed into the DOM (and hence the screen) is I/O, sure. But the creating / rendering of the template is a pure function, which is what we are dealing with here.