Themer.js

Spice up your app with dynamic themes.

Features:

• Automatic day/night switching using the sunset and sunrise times of the user's location
• System prefers-color-scheme support
• Android meta theme-color support
• Custom themes
• Manual control over everything

Demo

• https://themer.js.kmr.io

Examples

• Vue: themer.js/examples/vue
• React: themer.js/examples/react
• Svelte: themer.js/examples/svelte

Quick Start

Install

# using yarn
$ yarn add themer.js

# using npm
$ npm install themer.js

Define the light and dark themes

To use the auto or system themes, you must define a light and dark Theme object.

import Themer, { auto, system } from "themer.js";

const light = {
  "styles": {
    "css": {
      "--app-background-color": "#f1f1f1",
      "--primary-text-color": "#555"
    }
  }
}

const dark = {
  "styles": {
    "css": {
      "--app-background-color": "#242835",
      "--primary-text-color": "#f1f1f1"
    }
  }
}

// instantiate Themer.js
const themer = new Themer({
  themes: { light, dark, auto, system }
});

Setting a theme

import Themer, { auto, system } from "themer.js";
import { light, dark, auto, system } from "./themes/index.js";

const themer = new Themer({
  themes: { light, dark }
});

// set theme to dark
themer.set(dark);

// set theme to auto
themer.set(auto);

// set theme to system
themer.set(system);

Setting a custom theme

Pass a valid Theme object to Themer.set().

import Themer from "themer.js";

const custom = {
  "styles": {
    "css": {
      "--app-background-color": "#f1f1f1",
      "--primary-text-color": "#555"
    }
  }
};

const themer = new Themer();

themer.set(custom);

API

Themer( config )

• Arguments:

  • {Object} config

• Details: Instantiate Themer.js.

• Usage:

  import Themer, { auto, system } from "themer.js";
  import { light, dark, custom } from "./themes/index.js";
  
  const config = {
    debug: true,
    onUpdate: (theme) => console.log(theme),
    themes: { light, dark, auto, system, custom }
  };
  
  const themer = new Themer(config);
  

• See also: Config object

Themer.set( theme )

• Arguments:

  • {Object} theme

• Details: Sets the active theme.

• Restrictions:

  • auto|system: Both light and dark themes must be defined in the Config object.
  • auto: Requires user geolocation consent.
  • system: The browser must support prefers-color-scheme.

• Usage:

  const dark = {
    "styles": {
      "css": {
        "--app-background-color": "#242835"
      }
    }
  };
  
  Themer.set(dark);
  

• See also: Theme object

Themer.themeSupportCheck()

• Details: Helper function to determine browser support for the system theme.

• Returns: boolean

• Usage:

  // Chrome 76, Firefox 67, Safari 12.1
  Themer.themeSupportCheck();
  ↳ true
  
  // unsupported browsers
  Themer.themeSupportCheck();
  ↳ false
  

• See also: prefers-color-scheme

Config object

Key	Type	Description
debug	boolean	Log debug console statements.
onUpdate	function	A callback function that returns the set Theme object.
themes	object	The available Theme objects.

Example:

{
  debug: true,
  onUpdate: (theme) => console.log(theme),
  themes: { light, dark, auto, system, custom }
}

Theme object

Key	Type	Description
styles	`object	string`

Examples:

{
  "styles": {
    "android": "#f1f1f1",
    "css": {
      "--app-background-color": "#f1f1f1",
      "--primary-text-color": "#555"
    }
  }
}

{
  "styles": "auto"
}

Styles object

The theme styles. Feel free to add more key/value pairs and use the onUpdate callback to get the active theme. You can use the active theme object in other parts of your application. For example, if you want to have different Google Maps themes for light and dark themes, you can add a new key to the Styles object called googleMaps and store the Google Maps style array there. This allows you to get the appropriate styles even when using auto and system themes.

Key	Type	Description
android	string	Sets the meta theme-color.
css	object	The theme CSS variables.

Example:

{
  "styles": {
    "android": "#f1f1f1",
    "css": {
      "--app-background-color": "#f1f1f1",
      "--primary-text-color": "#555"
    }
  }
}

Preset Themes ( auto|dark )

To use auto and system themes, both a light and dark theme must be defined in the Config object

• Details:
  • auto: Sets light during the day and dark during the night.
  • system: Sets to system theme preference. (light|dark)
• Restrictions:
  • auto|system: Both light and dark themes must be defined in the Config object.
  • auto: Requires user geolocation consent.
  • system: The browser must support prefers-color-scheme.

CSS Variables

Use the CSS variables defined in your Styles object anywhere in your application and it will update in real time to the corresponding theme variable.

html {
  background-color: var(--app-background-color);
  color: var(--primary-text-color);
}