import-maps VS es-module-shims

Long time huge fan of JS. I appreciate your calling out the multi-paradigm aspect; having these first class functions & prototype based inheritance has been so flexible.

TC39 has done a great job shaping the language over the years. New capabilities are usually well thought out & integrate well. Async await has been amazing.

The one major miss that makes me so sad and frustrated is modules; js has gotten better everywhere except it's near requirement for build tooling. Being able to throw some scripts on a page and go is still an unparalleled experience in the world, is so direct & tactile an experience. EcmaScript Modules was supposed to improve things, help get us back, but imports using url specifiers made the whole thing non-modular, was a miss. We're still tangled & torn. Import-maps has finally fixed but it's no where near as straightforward, and it still doesn't work in workers, which leaves us infuriatingly shirt of where the past was. https://github.com/WICG/import-maps/issues/2

makes sure your app is getting the download it expects. Adoption is probably pretty minimal though. https://developer.mozilla.org/en-US/docs/Web/Security/Subres...

I think the big thing making this unlikely though is that very few folks use cdns these days. We designed ESM as a module system for the language, but then took a good fraction of a decade to build import-maps, to let us actually use modules in a modular way. Good news, we can finally use modules modularly! https://caniuse.com/import-maps

Bad news? Oh import-maps only works for the simplest case. Doesn't work in webworkers/service workers. https://github.com/WICG/import-maps/issues/2

The point is that single page apps almost always are bundled together, as using CDNs hasn't even been technically possible.

Also, CDNs are kind of somewhat pointless, now that http caches are partitioned by origin (for security reasons). They might have better anycast infrastructure to get the content out faster, but without the caching there's no inherent advantage. The user will download the same jquery file again in each site they go to, no already having it cached anymore. Bah humbug!

https://github.com/WICG/import-maps/issues/2

Bare specifiers has been the tragedy of ESM. Nice module syntax... that is utterly u deoyable & which has had to have awful de-modularizing specifiers hard-coded into each file to make it work. Abominable sin to introduce "modules" to JS/es2015 then spend a decade dragging everyone along with no story for how to have modular modules.

Import-maps are like "here" to fix this on the web... finally... except they only are shipping to the happiest sunniest easiest case, with Web Workers being totally shit out of luck in spite of some very simple straightforward suggested paths forward. https://github.com/WICG/import-maps/issues/2

I think Deno is making pretty good tradeoffs along the way here. This looks like package.json at surface level, but there is a nightmare of complexity under the surface. Typescript, ESM, cjs all have various pressures they create & in Node it's just incredibly tight & tense dealing with packaging, where-as Deno's happy path of Typescript first does not slowly tatters one over time. It really has been super pleasant being free of the previous world, and having something much more web-platform centric, more intented, with less assembly & less building, and more doing the actual coding.

I really hope import-maps eventually get broader support. Maybe this long-dwelling webworker issue should be brought up with WinterCG.

Import maps proposal

The concept of Import Maps was born in 2018 and made its long way until it was declared a new web standard implemented by Chrome in 2021 and some other browsers.

For package managers, you can use something like import maps to let the user specify which path points to what package, and resolve it properly.

Huh. I was about to complain that this breaks with web standards, but apparently it's being proposed as a standard feature: https://github.com/WICG/import-maps

Interesting!

For full compatibility and extra features, we usually use the library es-module-shims.

You can polyfill for unsupported browsers, it works surprisingly well: https://github.com/guybedford/es-module-shims

https://github.com/guybedford/es-module-shims has a polyfill. (But it is fairly large: 53KB raw, 15KB gzipped, 32KB minified, 11KB minified+gzipped. It’s providing a lot of likely-unnecessary functionality. I’d prefer a stripped-down polyfill that can also be lazily-loaded, controlled by a snippet of at most a few hundred bytes that you can drop into the document, only loading the polyfill in the uncommon case that it’s needed—like how five years ago as part of modernising some of the code of Fastmail’s webmail, I had it fetch and execute core-js before loading the rest iff !Object.values (choosing that as a convenient baseline), so that the cost to new browsers of supporting old browsers was a single trivial branch, and maybe fifty bytes in added payload.)

If we call the shim a framework, would you be ok with it then?

If you want import maps to be supported in any browser, there is an ES Module Shims polyfill which is compatible with any browser that has baseline ES Module Support (i.e. Edge 17+, Firefox 60+, Safari 10.1+, and Chrome 61+).

An example of a polyfill that can be used is the ES Module Shims polyfill that adds support for import maps and other new module features to any browser with baseline support for ES modules (about 94% of browsers). All you need to do is include the es-module-shim script in your HTML file before your import map script:

i often use es-module-shims so i can load npm packages in browsers without a bundler 😎

I explored using client-side service workers for build-less deployment workflows a while back, but the blocker was the initial visit when the service worker hasn't been installed yet. Ended up using es-module-shim's fetch hook (https://github.com/guybedford/es-module-shims#fetch-hook) instead, which worked quite well.

I kept the demo repo around here, in case it's helpful to anyone: https://github.com/lewisl9029/buildless-hot-reload-demo.

The repo itself is quite out of date at this point, but my current project, Reflame, is essentially the spiritual successor: https://reflame.app/

Reflame has the same ideals of achieving the developer experience I've always wanted for building client rendered React apps:

- instant production deployments (usually <200ms)

- instant preview environments that match production in pretty much every imaginable way (including the URL), that can also be flipped into development mode for fast-refresh (for the seamless feedback loop we're used to in local dev) and dev-mode dependencies (for better error messaging, etc)

- close-to-instant browser tests (1-3 seconds) that enable image snapshot comparisons that run with maximum parallelism and only rerun when their dependency graphs change

The problem of course is that browser-support for Import Maps is sadly lacking (only Chrome/Chromium-based at time of writing). There are tricks/shims to get around this, like ES-Module-Shims. I find these approaches to be a little too intrusive, personally.