Slab
All components

Form

Rating

A row of native radios from 1 to max, with one label and one value, that previews the value under the pointer.

Element
<slab-rating>
Built on
[role=radiogroup] + <input type=radio>s
As Markdown
rating.md

Example

Here's a styled version, <slab-styled-rating>. It's not in the package — it's an example of what you can build with the headless element. Copy it and make it yours at the bottom of this page. Switch to "As it ships" to see the same markup with the headless element and no CSS at all. That's your starting point.

Styled example As it ships
How smooth the slab came out of the trowel.
HTML
<slab-styled-rating label="Finish" step="0.5" value="3.5">
  <span slot="description">How smooth the slab came out of the trowel.</span>
</slab-styled-rating>
How smooth the slab came out of the trowel.
HTML
<slab-rating label="Finish" step="0.5" value="3.5">
  <span slot="description">How smooth the slab came out of the trowel.</span>
</slab-rating>

Usage

Install
pnpm add slab-elements lit
HTML
<script type="module">
  import 'slab-elements/rating.js';
</script>

<slab-rating label="Rating" name="rating" value="3"></slab-rating>

Nothing is drawn, so give each ::part(star) a look, and ::part(filled) the look of the value. The radios are named by their numbers and the group by label, so a screenreader reads “Rating, 3, radio button, 3 of 5”. While the pointer is over a radio, the radios up to it are filled instead and the host is :state(previewing), which can tell a preview apart from the value.

With step="0.5", each star is two radios, named “0.5”, “1”, “1.5” and so on, and the value can be a half. A star’s first radio is also ::part(start) and its second ::part(end), so style each as half of a star, such as by clipping each to its half.

Keyboard

Key What it does
Tab Moves into the rating at the checked radio, or the first, and out.
Up, Down, Left, Right Moves to the previous or next radio and checks it.
Space Checks the focused radio.
Enter Submits the form, as on a native radio.

Behavior

A rating with no visual styles: a row of native radios, one for each point from 1 to max, with one label, one value, and one validity for all of them. With step="0.5", there's one for each half point instead, two to a star.

The radios are the platform's, in the shadow root, so they're checked, moved between with the arrow keys, and read the way a native radio group is. Each is named by its number, and the group by label, so a screenreader reads "Label, 3, radio button, 3 of 5".

Each radio is a star part. Those up to the value are filled as well, and while one is hovered, those up to it are filled instead, so a pointer previews the value it would pick. The host is :state(previewing) while it does. Nothing is drawn, so a star, a heart, or a radio button is yours to decide. With half steps, each star's two radios are its start and end halves, so a half-filled star is a filled start beside an unfilled end.

Style it through its parts and through :state(disabled), :state(error), :state(previewing), and :state(required). How the radios are arranged is layout, so it's left to the styles around them.

API

<slab-rating>

Attributes
Name Type Default Description
label Required string
disabled boolean false
hide-label boolean false
max number 5 How many stars there are. Anything but a whole number of 1 or more is 5.
name string ''
required boolean false
step 1 | 0.5 1 1 for whole stars, or 0.5 for half stars. Anything else is 1.
value string '' The checked radio's number. Like a native input, the attribute is the default value and the property is the current one. A value that isn't one of the radios' numbers, from step to max, checks nothing and reads back as an empty string.
version string
Properties
Name Type Description
form Read-only HTMLFormElement | null
validity Read-only ValidityState
Methods
Signature Description
checkValidity(): boolean
focus(options?: FocusOptions): void
reportValidity(): boolean
resetValidityFeedback(): void Clears the validity feedback without changing validity.
setCustomValidity(message: string): void
setValidity(flags?: ValidityStateFlags, message?: string): void
Events
Name Type Description
input Event
change Event
Slots
Name Type Description
description Element | string
CSS parts
Name Description
description Text about the rating, and its validity message when it has one
end With half steps, the radio for the second half of a star
filled Each radio up to the value, or up to the hovered one
label The label
star Each radio
stars The radios
start With half steps, the radio for the first half of a star
validity-message

Copy and own it

<slab-styled-rating> isn't in the package. It's an example — copy it into your project and change whatever you want. Under the hood, it's just the headless element, subclassed, with styles set. That's it. Keyboard, focus, ARIA, forms, and events all come from the headless element, and the styles only reach in through ::part() and :state(), same as yours would.

To use it, copy these files, swap the tag in @customElement() for one of your own, and import it. tokens.styles.ts holds the colors and fonts every styled example shares, so you only need it once.

rating.ts 
import { customElement } from 'lit/decorators.js';
import Rating from 'slab-elements/rating.js';
import styles from './rating.styles.js';
import tokens from './tokens.styles.js';

declare global {
  interface HTMLElementTagNameMap {
    'slab-styled-rating': StyledRating;
  }
}

/**
 * Rating, styled: a course of bricks, laid in ember up to the value. With half
 * steps, each brick is split in two.
 */
@customElement('slab-styled-rating')
export default class StyledRating extends Rating {
  static override styles = [tokens, styles];
}
rating.styles.ts 
import { css } from 'lit';

export default css`
  :host {
    color: var(--ink);
    display: grid;
    font-family: var(--font-body);
  }

  [part~='label'] {
    font-family: var(--font-display);
    font-size: 1.0625rem;
    font-weight: 600;
    margin-block-end: 0.5rem;
  }

  :host(:state(required)) [part~='label']::after {
    color: var(--ember-deep);
    content: ' *' / '';
  }

  [part~='stars'] {
    display: flex;
    gap: 0.375rem;
  }

  [part~='star'] {
    appearance: none;
    background-color: var(--paper);
    block-size: 1.5rem;
    border: var(--border);
    border-radius: 0;
    box-sizing: border-box;
    cursor: pointer;
    inline-size: 2.75rem;
    margin: 0;

    &:focus-visible {
      outline: 3px solid var(--ember);
      outline-offset: 3px;
    }

    &:disabled {
      cursor: not-allowed;
      opacity: 0.5;
    }
  }

  /*
    Half steps split each brick in two, butted together across the gap,
    with a thin seam between the halves.
  */
  [part~='start'] {
    border-inline-end-width: 1px;
    inline-size: 1.375rem;
  }

  [part~='end'] {
    border-inline-start-width: 1px;
    inline-size: 1.375rem;
    margin-inline-start: -0.375rem;
  }

  [part~='filled'] {
    background-color: var(--ember);
  }

  /*
    A lighter course while previewing, so what's hovered reads as a
    preview rather than as the value.
  */
  :host(:state(previewing)) [part~='filled'] {
    background-color: color-mix(in srgb, var(--ember) 55%, var(--paper));
  }

  /*
    Spaced by what's in it rather than by a gap, so a description with
    nothing in it takes no room.
  */
  [part~='description'] {
    color: var(--ash);
    display: grid;
    font-size: 0.875rem;
  }

  ::slotted([slot='description']) {
    margin-block-start: 0.375rem;
  }

  [part~='validity-message'] {
    color: var(--ember-deep);
    font-weight: 600;
    margin-block-start: 0.375rem;

    &::before {
      content: '■ ' / '';
    }
  }
`;
tokens.styles.ts 
import { css } from 'lit';

/*
  The styled components' palette and type, taken from the logo: ink for the
  courses, ember for the base, paper behind them.

  Each is a short alias for a "--slab-styled-*" property, with the default as
  its fallback. Retheming is "--slab-styled-ember" and the rest on ":root",
  which every shadow root inherits. Were the defaults declared under those
  names here instead, each host's own declaration would shadow the page's.

  Each default is "light-dark()", so the components follow the page's
  "color-scheme": "dark" for dark, "light" for light, and "light dark" to
  follow the operating system. Ink and paper trade places in the dark, so
  ink is always the text and paper always what's behind it. Contrast is given
  as light, then dark.
*/
export default css`
  :host {
    /* Secondary text. 6.8:1 and 6.9:1 on paper. */
    --ash: var(--slab-styled-ash, light-dark(#5e5a55, #a8a19a));
    --border: 2px solid var(--ink);

    /* Behind disabled and read-only controls, and hovered rows. */
    --chalk: var(--slab-styled-chalk, light-dark(#f4f1ec, #2b2926));

    /*
      The logo's orange, brighter in the dark. 4.25:1 and 5.2:1 on paper is
      enough for borders, fills and large text, but not always for small text,
      which takes "--ember-deep".
    */
    --ember: var(--slab-styled-ember, light-dark(#d9492a, #ec5f3b));

    /*
      Orange for small text on paper, and for paper text on it. 5.7:1 and
      7.4:1.
    */
    --ember-deep: var(--slab-styled-ember-deep, light-dark(#b3381a, #ff8566));
    --font-body: var(
      --slab-styled-font-body,
      'IBM Plex Sans',
      system-ui,
      sans-serif
    );
    --font-display: var(
      --slab-styled-font-display,
      'Zilla Slab',
      rockwell,
      'Roboto Slab',
      serif
    );
    --font-mono: var(
      --slab-styled-font-mono,
      'IBM Plex Mono',
      ui-monospace,
      monospace
    );
    --ink: var(--slab-styled-ink, light-dark(#1c1c1c, #f4f1ec));
    --paper: var(--slab-styled-paper, light-dark(#fff, #1a1918));

    /* The hard, offset shadow a raised surface casts. */
    --shadow: 4px 4px 0 var(--ink);
  }
`;