> Glimmer compiles your templates into low-level code so it can run as fast as possible—without sacrificing ease of use.
What's the benefit vs just writing your templates in JavaScript in the first place?
What's the benefit vs just writing your templates in JavaScript in the first place?
For me personally, templates ever-so-slightly edge out tools like JSX. For one, I subscribe to the Rule of Least Power[0]. Having the full expressiveness of JavaScript is very nice, but it makes it harder for tools to statically analyze and optimize the rendering process. Ember has gone through three major rendering engine architectures now (string-based, DOM-based and now the Glimmer VM) and the simplicity of the templating language has made that portability much easier.
[0]: https://www.w3.org/2001/tag/doc/leastPower.html
More importantly though, there are a lot of people in the world who know HTML and CSS. The fact that Glimmer templates are "just HTML" makes them accessible to people like designers who may not understand all of the fancy destructuring or array mapping happening in your JSX.
Lastly, and this is perhaps just a personal foible, but I have a really hard time mentally mapping more complicated JSX expressions into the final HTML output. It's fine when you're writing it, but reading it later, particularly to write CSS for it, is more challenging for me than Handlebars. I know some people would say that this is a code smell and that I should break that component up into smaller components, but I'd rather that decision be made by me than because I feel forced into it by the muddiness of my render() method.
As for mapping JSX to HTML I think React's biggest strength is it's composability. But it comes with a price: things start to smell very, very quickly unless you religiously separate concerns.
"Hummm, this string technology was meant for static webpages :( I think the solution is to create an arbitrary sub-language and add more string bits to it to make it dynamic" is more adapted when you quickly want to add a few dynamic behaviors to an existing static template here and there, but not so much when you build a complex app from the ground up.
Not to mention these opaque strings suck when you are serious about using a typed language :)
isn't this like, at least a little backwards? JSX is HTML and JS. templating languages are HTML with some custom DSL.
destructuring and especially mapping are pretty simple concepts. creating a new syntax to cater to people who couldn't learn one in the first place seems counterintuitive?
is teaching someone a for loop really at all (let alone significantly) easier than teaching them to map an array?
edit: "creating a new syntax to cater to people who couldn't learn one in the first place seems counterintuitive?" on second read this seems thoughtless. isn't that almost the whole point of a DSL? i think you and i have convinced myself to stop hating on templates.
"It's familiar good ol HTML" is marketing again.
The argument about underpowered templates being easier to optimize is true though (see svelte for another approach), but it doesn't seem to matter nowadays. Good luck finding an actual difference with a good virtual-dom lib (known for their GC demands) even on a low powered machine on a real app.
"JSX is a preprocessor step that adds XML syntax to JavaScript." http://buildwithreact.com/tutorial/jsx
Whereas the templates in Glimmer are built on HTML. At the 10,000 ft view, my two cents: it looks easier to reason about what is going on with dynamic elements in the template via handlebars together with what is going with the html elements themselves in terms of rendering/appearance/css, as compared to the JSX syntax.
i just can't convince myself "it looks less scary" is worthy of the technical tradeoffs (for me, at the very least).
I should have been clearer and said: it actually is easier to reason about the html and the dynamic rendering with the approach Glimmer takes.
Do this in a template for instance:
import range from 'lodash/range'
const Item = ({ number }) => <li>{number}</li>
const App = () => (
<ul>
{range(0, 20, 5)
.map(index =>
<Item number={index} />
)
}
</ul>
)
I use Pug/Jade, which always compiled to JS for speed and also supports Virtual DOM and server-side rendering. Pug can be written, understood, and updated by users who have no knowledge of JS but still gives me the full power of JS when necessary.