This addon can be used to set a data attribute in Storybook's iframe HTML element triggering a toggle between your custom themes.

Example styles:

:root [data-theme="theme1"] {
  --white: #000;
  --black: #fff;
}

:root [data-theme="theme2"] {
  --white: #fff;
  --black: #000;
}

:root [data-theme="theme3"] {
  --white: #696969;
  --black: #700404;
}

NPM / Yarn

npm i -D storybook-custom-theme-switcher

yarn add storybook-custom-theme-switcher -D

Add the addon to .storybook/main.js:

module.exports = {
  addons: ["storybook-custom-theme-switcher"],
};

Add parameters options to .storybook/preview.js:

export const parameters = {
  theme: {
    selector: "body",
    dataAttr: "data-theme",
    /* Put all theme options in
    themeOptions. You can name
    customeTheme as you want.*/
    themeOptions: {
      default: "", // empty string for option to get back to default theme 
      customeTheme1: "theme1",
      customeTheme2: "theme2",
      customeTheme3: "theme3",
    },
    defaultTheme: "",
  },
};

The theme parameter accept an array of Theme object.

Each Theme is an object with the following properties:

• selector (string - default: 'body'): Target element to which the data Attribute will be applied.
• dataAttr (string - default: 'data-theme'): The data attribute that will be applied.
• themeOptions ({ [key: string]: string } - default: {}): The themes you want to use as an Object.
• defaultTheme (string - default: ''): The name of the theme that should be used on default.

Click on the new theme popup in the toolbar in storybook to switch between your themes.