view-transitions VS msw

So let’s add the following CSS to the index template (Slim recognizes a css: block that just renders a normal tag):

/ app/views/counter/index.html.slim
/ (anywhere outside the Turbo Frame tag)
css:
  /* (1) */
  #counter {
    view-transition-name: counter;
    contain: layout;
  }

  /* (2) */
  @keyframes rotate-out {
    to {
      transform: rotate(90deg);
    }
  }

  @keyframes rotate-in {
    from {
      transform: rotate(-90deg);
    }
  }

  /* (3) */
  ::view-transition-old(counter) {
    animation-duration: 200ms;
    animation-name: -ua-view-transition-fade-out, rotate-out;
  }
  ::view-transition-new(counter) {
    animation-duration: 200ms;
    animation-name: -ua-view-transition-fade-in, rotate-in;
  }

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Let’s break this code down a bit:

1. The CSS selector #counter matches the counter div and the view-transition-name property names this area of the screen, for the purpose of View Transitions, as counter. This name will be used in the animation declarations below.

   The clone property currently must be added here for some reasons internal to the current View Transitions implementation in Chrome and must be set to paint or layout. This restriction is planned to be removed from the specification, though, and in fact I’ve heard that it is not needed in Chrome Canary any more.

2. The rotation animation keyframes are defined here. Note that while the transition also uses fade-in and fade-out animations, they don’t have to be defined here because the spec requires browsers to implement them natively under the name -ua-view-transition-fade-in/out.

3. The CSS animations for the counter (the View Transition area named counter) are configured here. The CSS selectors here are some of the pseudo-elements automatically created during the transition. The -old pseudo-element represents a screenshot of the old DOM state that should somehow disappear or ”go away“ from the viewport and the -new pseudo-element represents a live version of the final DOM state that should be brought into sight.

So, overall, this code selects a portion of the page and animates it independently from the rest of the page during Turbo Frames DOM updates. Behind the scenes, the default cross-fade for the rest of the page still also takes place, it just is not visible because all its elements are visually identical. The result looks like this:

A few initial tips & tricks

Does this work for Turbo Drive visits, too?

Sure it does and it’s actually pretty easy! All we have to do is define the same event handler as we did above but attach it to the turbo:before-render event instead. By default we’ll get a cross-fade animation of the whole page during Turbo Drive page visits.

Do not try to ”name“ the Turbo Frame itself

When playing with Turbo Frame View Transitions I first tried to use a custom animation for the whole Turbo Frame element by naming it via the view-transition-name property. For some reason, this does not work and you end up with a very cryptic and misleading error message in the console (yes I did have the contain property in the CSS declaration):

Aborting transition. Element must contain paint or layout for view-transition-name : counter

So, when using custom animations, an element from inside the Frame must be selected and named.

Debugging View Transitions

Since View Transitions are technically just normal CSS animations, they can be inspected with the Animations panel in the Dev Tools. Also, the automatically created pseudo-elements are visible in the Elements tab during the transitions:

Conclusions

I confess I am quite excited about the new View Transitions API. Among the things I particularly like about it are the following:

• It is surprisingly easy to plug this inside Hotwire Turbo and you get the default cross-fade transition animation immediately for free (in latest Chrome-like browsers, that is).
• Since this is implemented natively in the browser, the animations are highly optimized and performant.
• View Transitions should allow (today or in the future) building highly interactive transitions similar to those in Material Design.
• There is some initial support for Multi-Page Applications, too, which is great news because we can bring transition animations declared in CSS to our old but gold apps.
• It should be possible to use a different animation based on the ”direction“ of the visit (Back/Forward) using the Navigation API (also still experimental and not very well supported, though).

Things I am still concerned about:

• Browser support: the Firefox team evaluates it, the Safari team is silent. This will be a log run and making a polyfill is probably too difficult. For web sites where transition animations are critical, this is still a no go.

• If you’re not careful enough, the transition feels more fluid but also a little bit slower. The reason for it is that View Transitions start the animations at the moment when both the old and new DOM states are already rendered. This means that the exit animation is delayed until new content is available and until that time, nothing happens. Also, the entry animations for the new state usually delay its appearance a little bit more.

  This is not a problem of View Transitions themselves but rather a more generic one. If the exit animation (e.g. a fade out) started immediately after user interaction (e.g. a link click), sometimes the user would have to stare at a blank page until the new page content is grabbed, rendered and run through an entry animation. Still, some kind of support for this scenario (possibly with custom loaders or skeletons) would be nice.

• Tailwind support: I think the current Tailwind syntax does not allow targeting the HTML document-connected pseudo-elements so we have to resort to custom CSS (which is not a big problem, actually).

• All transitions target the whole page, there is currently no option to make, say, two components (Frames) animate totally independently. An initial proposal for ”scoped transitions“ can be found here.

Overall, I like this feature and wish it matures enough and gets wider support soon!

true, but HTML-only websites are often pretty clunky

infuriatingly, if HTML had just a bit more oomph, we could make a lot better websites with it, but they haven't been moving HTML forward as a hypermedia for decades now (see https://htmx.org for what I mean, they could implement this concept in the browser in a week, and it would change web development dramatically)

the upcoming view transitions API will help:

https://github.com/WICG/view-transitions

but, still, there are some really obvious and simple things that could be done to make HTML much more compelling (let's start by making PUT, PATCH and DELETE available in HTML!)

Cool answer: Look at shared element transition. this is gonna be really cool one day, sadly not yet out of the proposal state... https://github.com/WICG/shared-element-transitions

Native features faster: Quickest path to utilizing native features/UX improvements once they are released, no need to wait for a third party implementation. Example: shared element transitions first came to native, then were replicated on the web.

Lol yes, can’t edit now sorry.

1: https://github.com/WICG/shared-element-transitions

I took the experimental page transition API (a.k.a. shared element transitions) for a test drive with SvelteKit, and the result was pretty slick. You’ll need Chrome Canary with the chrome://flags/#document-transition flag enabled if you want to try this one out yourself — the original tweet has a video if you don’t want to jump through those hoops. There’s a live demo and a GitHub repo if you want to see how it was accomplished.

Here is link number 1 - Previous text "yet"

There's also the developer guide https://github.com/WICG/shared-element-transitions/blob/main/developer-guide.md.

However, I discovered a great combination that transformed my API call testing in TypeScript: Vitest and Mock Service Worker (MSW). Their well-crafted design makes them incredibly easy to use, enhancing the overall testing experience.

While mocks are effective, they require modifying the component's internal logic or mocking global functions like fetch. This can become cumbersome for complex components with numerous API interactions. Here's where MSW shines.

> For those wondering what the use case is, you must not have tried it. It does take work to set up (with each version that's less), but it can be very nice to test in isolation esp in cases where a component is under a login, the 4th page of a 10 page form, etc. Also obviously if you're working on a component library that ships without an app, Storybook can be your development and/or demo app.

I have worked with storybook extensively over the past couple of years and my team is moving away from it in favour of MSW (https://mswjs.io).

For "4th page of a 10 page form" during the development there's hot reloading which is really stable nowadays and haven't failed me, although I understand that some setups are old and it might be easier to configure Storybook than good hot reloading.

I'm not entirely sure about the testing part of it and I'd be grateful if you could elaborate. I haven't felt the need for some special setup with SB because for unit tests, I can test a deeply nested component separately. For E2E tests, I usually test the whole form.

I agree on the component library part, this is probably the only use case where Storybook is 100% justified, but I'm unconvinced about the

Additionally, thank you to all our community launch partners across the frontend ecosystem for helping us bring Storybook 8 to the world! Thanks to Chromatic, Figma, ViteConf, Omlet, DivRiots, story.to.design, StackBlitz, UXpin, Nx, Mock Service Worker, Anima, Zeplin, zeroheight, kickstartDS, and Kendo UI.

similar with msw.js, but fully automated

they could be network mocks (use msw)

With orval, we can also integrate the API client in our unit tests. Orval provides first class support for mocking through the (Mock Service Worker)[https://mswjs.io/] library, and it can automatically generate the MSW handlers for testing server.

Consider a hypothetical scenario where data from a list of companies within an ERP needs to be retrieved. As a personal recommendation, leverage tools like MSW for top-level mocks, which can significantly enhance the testing process.