Svelte OS Themes

Svelte 5 theme helper.

Installation

npm install svelte-os-themes

Usage

<!-- +layout.svelte -->
<script>
  import {ThemeProvider} from 'svelte-os-themes';

  let {children} = $props();
</script>

<ThemeProvider
  fallback="system"
  attribute="class"
  storageKey="theme"
  colorScheme={true}
  system={true}
  nonce=""
>
  {@render children()}
</ThemeProvider>

<!-- +page.svelte -->
<script>
  import {useTheme} from 'svelte-os-themes';

  let theme = useTheme();

  $inspect(theme.current);
</script>

<button
  type="button"
  onclick={function () {
    theme.current = 'light';
  }}
>
  Light
</button>
<button
  type="button"
  onclick={function () {
    theme.current = 'dark';
  }}
>
  Dark
</button>
<button
  type="button"
  onclick={function () {
    theme.current = 'system';
  }}
>
  System
</button>

API

ThemeProvider

• fallback

  The default theme to use when no theme is set in storage.

  accepted values: 'light', 'dark', 'system'
  default value: 'system'

• attribute

  The attribute to set on the html element.

  accepted values: 'class', 'data-<string>'
  default value: 'class'

• storageKey

  The key to use when storing the theme in localStorage.

  accepted values: <string>
  default value: 'theme'

• system

  Whether to change theme when os theme changes.

  accepted values: true, false
  default value: false

• colorScheme

  Whether to add/update the html's color-scheme.

  accepted values: true, false
  default value: true

• scriptNonce

  The nonce to use for script.

  accepted values: <string>
  default value:

• styleNonce

  The nonce to use for style.

  accepted values: <string>
  default value:

useTheme

useTheme does not accept any arguments and returns an object with the following properties:

• current

  Returns the current theme when used as a getter and sets the theme when used as a setter.

  <script>
    import {useTheme} from 'svelte-os-themes';
  
    let theme = useTheme();
  </script>
  
  <div>Current Theme: {theme.current}</div>
  
  <button
    type="button"
    onclick={function () {
      theme.current = 'light';
    }}
  >
    Light
  </button>
  <button
    type="button"
    onclick={function () {
      theme.current = 'light';
    }}
  >
    Dark
  </button>
  <button
    type="button"
    onclick={function () {
      theme.current = 'light';
    }}
  >
    System
  </button>

• getTriggerProps

  Returns attributes for button to be used to trigger a particular theme. eg:

  <script>
    import {useTheme} from 'svelte-os-themes';
  
    let theme = useTheme();
  </script>
  
  <button {...theme.getTriggerProps({value: 'light'})}>Light</button>
  <button {...theme.getTriggerProps({value: 'dark'})}>Dark</button>
  <button {...theme.getTriggerProps({value: 'system'})}>System</button>

  or set value to auto

  <script>
    import {useTheme} from 'svelte-os-themes';
  
    let theme = useTheme();
  </script>
  
  <button
    {...theme.getTriggerProps({
      value: 'auto',
      sequence: ['light', 'dark'],
    })}
  >
    {#if theme.current === 'light'}
      Go dark
    {:else if theme.current === 'dark'}
      Go light
    {/if}
  </button>

parseTheme

parseTheme is a helper function that parses any value into a valid theme. See example below

console.log(parseTheme('LIGHT')); // 'light'
console.log(parseTheme('invalid')); // undefined
console.log(parseTheme('invalid', 'dark')); // 'dark'