#Skeleton

#Description

The Skeleton component is a visual building block helper. It will provide loading placeholders that display a non-interactive preview of the app’s actual UI to visually communicate that content is being processed.

#Take in consideration

It has to be used carefully and not as a quick loading indicator replacement. The reason lays in that, that the browser will use additional resources to render the additional state. And if it is misused, like showing not a nearly identical UI or it is shown for just a fraction of a second, then it will rather distract the user experience, than enhance it.

Also, the fact, that in some setups, the user is first downloading almost the whole web application before we actually are able to show some skeletons during the API calls.

#Gatsby

Gatsby as a framework makes the perfect fit to utilize a good skeleton user experience from the very first-page visit. Every page is optimized to load as fast as possible (in addition to page preloading and PWA). We can take advantage of this and show our skeleton as our initial state.

1. The skeletons will show up during the very first paint – even without JavaScript enabled.
2. Next, our page loads the needed application bundle, so we can start an API call, getting our user data.
3. Now our applications renders.
4. And finally, we have the user data to display.

#Accessibility

• Elements and components should be still responsive to screen width and font-size.
• Screen readers will get a mention that the loading state has finished as a aria-live update.
• Components and interactive elements are not accessible for keyboard users.

#When not to use

• For low-traffic pages, such as super-user-only admin pages, use a loading spinner instead.
• For a tiny, inline action or feedback, e.g. clicked a button and the action will take time, use the ProgressIndicator instead (animation).
• For fast processes that take less than 300ms, consider the ProgressIndicator or no loading state at all.
• For a background process or a long-running process, e.g. importing data or exporting reports, use the ProgressIndicator instead (percentage).

#When to use

• Use on high-traffic pages and landing pages, if they require a loading state.
• Use when there’s more than one element loading at the same time that requires an indicator.
• Use when the process would take more than 300ms to load on an average internet connection.
• Use the Skeleton component when the ProgressIndicator is not prominent enough.

#How to use

You can use the Skeleton component as a provider for all underlying components, like inputs and buttons. This way, you can simply toggle on and off the skeletons. And all the spacing and sizing will be given from the components themselves.

But you can also use the Skeleton component to show a fake article or other figures.

#How it works

Every Eufemia component should support a skeleton natively. But for simplification, you can use the Skeleton component as a provider, so enable the skeletons for a group of components.

If you use the skeleton as a provider, the Space component is used as a wrapper. This wrapper also serves the underlying components to define the style type or animation. If only the defaults are used, then you can skip it by setting the element to false element={false}.

But the Skeleton component also supports a set of ready-to-use figures. Use it like figure="article".

<Div id="your-app">
  <Skeleton show={true}>
    <Input>I'm hidden behind the skeleton</Input>
    <Input>I'm hidden behind the skeleton</Input>
  </Skeleton>
</Div>

#Global Provider

You can also use the global Eufemia Provider to enable the underlying skeletons. You can even have multiple providers wrapped.

<Provider locale="nb-NO">
  <Div id="your-app">
    <Provider skeleton={true}>
      <Input>I'm hidden behind the skeleton</Input>
      <Input>I'm hidden behind the skeleton</Input>
    </Provider>
  </Div>
</Provider>

#Exclude a part

You can easily exclude a part from being transformed to a skeleton by using Skeleton.Exclude.

<Skeleton show={true}>
  <Input>I'm hidden behind the skeleton</Input>

  <Skeleton.Exclude>
    <Input>I'm NOT hidden</Input>
  </Skeleton.Exclude>
</Skeleton>

#Suspense

You can take advantage of an async component by using the React Suspense with a skeleton fallback.

<Suspense
  fallback={
    <Skeleton show={true}>
      <Div id="user-data" />
    </Skeleton>
  }
>
  <Div id="user-data" />
</Suspense>

#Create a custom skeleton

In order to create the same skeletons as the build-ins, you can make use of a couple of helper tools.

function Component({ skeleton = false, ...params } = {}) {
  const context = React.useContext(Context)

  // Handle accessibility features
  skeletonDOMAttributes(params, skeleton, context)

  // Handle CSS classes – use either "shape" or "font"
  const className = createSkeletonClass('font', skeleton, context)
  return (
    <div {...params} id="my-component" className={className}>
      Hello World
    </div>
  )
}
render(<Component />)

SyntaxError: Unexpected token (15:1)

#Demos

#Input with Skeleton

<Input label="Input" skeleton />

#Toggle skeleton on/off

const UserData = () => {
  const [state, setState] = React.useState(true)
  return (
    <Skeleton show={state}>
      <H2 top bottom>
        Heading
      </H2>
      <P top bottom>
        Paragraph Non habitasse ut nisi dictum laoreet ridiculus dui.
      </P>
      <Input label_direction="vertical" label="Input" />
      <Skeleton.Exclude>
        <ToggleButton
          checked={state}
          on_change={({ checked }) => setState(checked)}
          top="large"
        >
          Toggle
        </ToggleButton>
      </Skeleton.Exclude>
    </Skeleton>
  )
}
render(<UserData />)

SyntaxError: Unexpected token (1:3)

#Skeleton wrapper

<Skeleton show>
  <H2 top bottom>
    Heading
  </H2>
  <P top bottom>
    Paragraph Non habitasse ut nisi dictum laoreet ridiculus dui.
  </P>
  <Button>Button</Button>
</Skeleton>

#Skeleton using Eufemia Provider

You can also use formElement={{ skeleton: true }}.

<Provider skeleton={true}>
  <H2 top bottom>
    Heading
  </H2>
  <P top bottom>
    Paragraph Non habitasse ut nisi dictum laoreet ridiculus dui.
  </P>
  <Button>Button</Button>
</Provider>

#Skeleton figures

You may import a given figure, or create your own.

import { Article } from '@dnb/eufemia/components/skeleton/figures'

<Skeleton show figure={<Article rows={5} />}>
  hidden content
</Skeleton>