@storybook/addon-knobs

What is @storybook/addon-knobs?

@storybook/addon-knobs is a Storybook addon that allows you to dynamically edit React component props using the Storybook UI. This makes it easier to experiment with different prop values and see the results in real-time.

What are @storybook/addon-knobs's main functionalities?

Text Knob

The Text Knob allows you to edit text props dynamically. In this example, the 'label' prop of MyComponent can be edited in the Storybook UI.

import React from 'react';
import { withKnobs, text } from '@storybook/addon-knobs';
import { storiesOf } from '@storybook/react';

const MyComponent = ({ label }) => <div>{label}</div>;

storiesOf('MyComponent', module)
  .addDecorator(withKnobs)
  .add('default', () => <MyComponent label={text('Label', 'Hello Storybook')} />);

Boolean Knob

The Boolean Knob allows you to toggle boolean props dynamically. In this example, the 'isVisible' prop of MyComponent can be toggled in the Storybook UI.

import React from 'react';
import { withKnobs, boolean } from '@storybook/addon-knobs';
import { storiesOf } from '@storybook/react';

const MyComponent = ({ isVisible }) => (isVisible ? <div>Visible</div> : <div>Hidden</div>);

storiesOf('MyComponent', module)
  .addDecorator(withKnobs)
  .add('default', () => <MyComponent isVisible={boolean('Is Visible', true)} />);

Number Knob

The Number Knob allows you to edit number props dynamically. In this example, the 'count' prop of MyComponent can be edited in the Storybook UI.

import React from 'react';
import { withKnobs, number } from '@storybook/addon-knobs';
import { storiesOf } from '@storybook/react';

const MyComponent = ({ count }) => <div>Count: {count}</div>;

storiesOf('MyComponent', module)
  .addDecorator(withKnobs)
  .add('default', () => <MyComponent count={number('Count', 42)} />);

Select Knob

The Select Knob allows you to choose from a set of predefined options. In this example, the 'color' prop of MyComponent can be selected from a list of colors in the Storybook UI.

import React from 'react';
import { withKnobs, select } from '@storybook/addon-knobs';
import { storiesOf } from '@storybook/react';

const MyComponent = ({ color }) => <div style={{ color }}>Colored Text</div>;

const options = {
  Red: 'red',
  Blue: 'blue',
  Green: 'green'
};

storiesOf('MyComponent', module)
  .addDecorator(withKnobs)
  .add('default', () => <MyComponent color={select('Color', options, 'red')} />);

Other packages similar to @storybook/addon-knobs

@storybook/addon-controls

@storybook/addon-controls is a more modern alternative to @storybook/addon-knobs. It provides a more intuitive and powerful way to interact with component props, including support for complex data structures and better integration with TypeScript.

react-live

react-live is a library for live editing React code with a focus on simplicity and performance. It allows you to embed live code editors in your documentation or Storybook, providing a more interactive experience compared to @storybook/addon-knobs.

react-view

react-view is a React component playground that allows you to live-edit code and props. It is similar to @storybook/addon-knobs but offers a more comprehensive set of features, including support for TypeScript and custom editors.

README

Storybook Addon Knobs (deprecated)

We are deprecating Knobs in favor of @storybook/addon-controls.

Discussion: https://github.com/storybookjs/storybook/discussions/15060

Storybook Addon Knobs allow you to edit props dynamically using the Storybook UI. You can also use Knobs as a dynamic variable inside stories in Storybook.

Framework Support.

This is what Knobs looks like:

Checkout the above Live Storybook or watch this video.

Getting Started

First of all, you need to install Knobs into your project as a dev dependency.

yarn add @storybook/addon-knobs --dev

The latest version of this addon supports Storybook v7. If you're using a previous version of Storybook you need to install the matching version of this addon, eg @storybook/addon-knobs@6.4.0.

within .storybook/main.js:

module.exports = {
  addons: ['@storybook/addon-knobs'],
};

Now, write your stories with Knobs.

With React

import React from 'react';
import { withKnobs, text, boolean, number } from '@storybook/addon-knobs';

export default {
  title: 'Storybook Knobs',
  decorators: [withKnobs],
};
// Add the `withKnobs` decorator to add knobs support to your stories.
// You can also configure `withKnobs` as a global decorator.

// Knobs for React props
export const withAButton = () => (
  <button disabled={boolean('Disabled', false)}>{text('Label', 'Hello Storybook')}</button>
);

// Knobs as dynamic variables.
export const asDynamicVariables = () => {
  const name = text('Name', 'James');
  const age = number('Age', 35);
  const content = `I am ${name} and I'm ${age} years old.`;

  return <div>{content}</div>;
};

With Vue.js

MyButton.story.js:

import { storiesOf } from '@storybook/vue';
import { withKnobs, text, boolean } from '@storybook/addon-knobs';

import MyButton from './MyButton.vue';

export default {
  title: 'Storybook Knobs',
  decorators: [withKnobs],
};

// Assign `props` to the story's component, calling
// knob methods within the `default` property of each prop,
// then pass the story's prop data to the component’s prop in
// the template with `v-bind:` or by placing the prop within
// the component’s slot.
export const exampleWithKnobs = () => ({
  components: { MyButton },
  props: {
    isDisabled: {
      default: boolean('Disabled', false),
    },
    text: {
      default: text('Text', 'Hello Storybook'),
    },
  },
  template: `<MyButton :isDisabled="isDisabled">{{ text }}</MyButton>`,
});

MyButton.vue:

<template>
  <button :disabled="isDisabled">
    <slot></slot>
  </button>
</template>

<script>
export default {
  props: {
    isDisabled: {
      type: Boolean,
      default: false,
    },
  },
};
</script>

With Angular

import { storiesOf } from '@storybook/angular';
import { boolean, number, text, withKnobs } from '@storybook/addon-knobs';

import { Button } from '@storybook/angular/demo';

export default {
  title: 'Storybook Knobs',
  decorators: [withKnobs],
};

export const withKnobs = () => ({
  component: Button,
  props: {
    text: text('text', 'Hello Storybook'), // The first param of the knob function has to be exactly the same as the component input.
  },
});

With Ember

import { withKnobs, text, boolean } from '@storybook/addon-knobs';
import { hbs } from 'ember-cli-htmlbars';

export default {
  title: 'StoryBook with Knobs',
  decorators: [withKnobs],
};

export const button = () => ({
  template: hbs`
    <button disabled={{disabled}}>{{label}}</button>
  `,
  context: {
    label: text('label', 'Hello Storybook'),
    disabled: boolean('disabled', false),
  },
});

Categorization

Categorize your Knobs by assigning them a groupId. When a groupId exists, tabs will appear in the Knobs storybook panel to filter between the groups. Knobs without a groupId are automatically categorized into the ALL group.

export const inGroups = () => {
  const personalGroupId = 'personal info';
  const generalGroupId = 'general info';

  const name = text('Name', 'James', personalGroupId);
  const age = number('Age', 35, { min: 0, max: 99 }, personalGroupId);
  const message = text('Hello!', 35, generalGroupId);
  const content = `
    I am ${name} and I'm ${age} years old.
    ${message}
  `;

  return <div>{content}</div>;
};

You can see your Knobs in a Storybook panel as shown below.

Available Knobs

These are the Knobs available for you to use. You can import these Knobs from the @storybook/addon-knobs module. Here's how to import the text Knob.

import { text } from '@storybook/addon-knobs';

Just like that, you can import any other following Knobs:

text

Allows you to get some text from the user.

import { text } from '@storybook/addon-knobs';

const label = 'Your Name';
const defaultValue = 'James';
const groupId = 'GROUP-ID1';

const value = text(label, defaultValue, groupId);

boolean

Allows you to get a boolean value from the user.

import { boolean } from '@storybook/addon-knobs';

const label = 'Agree?';
const defaultValue = false;
const groupId = 'GROUP-ID1';

const value = boolean(label, defaultValue, groupId);

number

Allows you to get a number from the user.

import { number } from '@storybook/addon-knobs';

const label = 'Age';
const defaultValue = 78;
const groupId = 'GROUP-ID1';

const value = number(label, defaultValue);

For use with groupId, pass the default options as the third argument.

const value = number(label, defaultValue, {}, groupId);

number bound by range

Allows you to get a number from the user using a range slider.

import { number } from '@storybook/addon-knobs';

const label = 'Temperature';
const defaultValue = 73;
const options = {
  range: true,
  min: 60,
  max: 90,
  step: 1,
};
const groupId = 'GROUP-ID1';

const value = number(label, defaultValue, options, groupId);

color

Allows you to get a colour from the user.

import { color } from '@storybook/addon-knobs';

const label = 'Color';
const defaultValue = '#ff00ff';
const groupId = 'GROUP-ID1';

const value = color(label, defaultValue, groupId);

object

Allows you to get a JSON object or array from the user.

import { object } from '@storybook/addon-knobs';

const label = 'Styles';
const defaultValue = {
  backgroundColor: 'red',
};
const groupId = 'GROUP-ID1';

const value = object(label, defaultValue, groupId);

Make sure to enter valid JSON syntax while editing values inside the knob.

array

Allows you to get an array of strings from the user.

import { array } from '@storybook/addon-knobs';

const label = 'Styles';
const defaultValue = ['Red'];
const groupId = 'GROUP-ID1';

const value = array(label, defaultValue);

While editing values inside the knob, you will need to use a separator. By default it is a comma, but this can be overridden by passing a separator variable.

import { array } from '@storybook/addon-knobs';

const label = 'Styles';
const defaultValue = ['Red'];
const separator = ':';
const value = array(label, defaultValue, separator);

For use with groupId, pass the default separator as the third argument.

const value = array(label, defaultValue, ',', groupId);

select

It allows you to get a value from a select box from the user.

import { select } from '@storybook/addon-knobs';

const label = 'Colors';
const options = {
  Red: 'red',
  Blue: 'blue',
  Yellow: 'yellow',
  Rainbow: ['red', 'orange', 'etc'],
  None: null,
};
const defaultValue = 'red';
const groupId = 'GROUP-ID1';

const value = select(label, options, defaultValue, groupId);

Options can also be an array:

import { select } from '@storybook/addon-knobs';
const label = 'Cats';
const options = ['linus', 'eleanor', 'lover'];
const defaultValue = 'eleanor';
const groupId = 'GROUP-ID2';
const value = select(label, options, defaultValue, groupId);

Options can also be an array OF objects:

const label = 'Dogs';
const arrayOfObjects = [
  {
    label: 'Sparky',
    dogParent: 'Matthew',
    location: 'Austin',
  },
  {
    label: 'Juniper',
    dogParent: 'Joshua',
    location: 'Austin',
  },
];
const defaultValue = arrayOfObjects[0];
const groupId = 'GROUP-ID3';
const value = select(label, arrayOfObjects, defaultValue, groupId);

radio buttons

It allows you to get a value from a list of radio buttons from the user.

import { radios } from '@storybook/addon-knobs';

const label = 'Fruits';
const options = {
  Kiwi: 'kiwi',
  Guava: 'guava',
  Watermelon: 'watermelon',
};
const defaultValue = 'kiwi';
const groupId = 'GROUP-ID1';

const value = radios(label, options, defaultValue, groupId);

options

Configurable UI for selecting a value from a set of options.

import { optionsKnob } from '@storybook/addon-knobs';

const label = 'Fruits';
const valuesObj = {
  Kiwi: 'kiwi',
  Guava: 'guava',
  Watermelon: 'watermelon',
};
const defaultValue = 'kiwi';
const optionsObj = {
  display: 'inline-radio',
};
const groupId = 'GROUP-ID1';

const value = optionsKnob(label, valuesObj, defaultValue, optionsObj, groupId);

Alternatively you can use this import:

import { optionsKnob as options } from '@storybook/addon-knobs';

...

const value = options(label, valuesObj, defaultValue, optionsObj, groupId);

The display property for optionsObj accepts:

• radio
• inline-radio
• check
• inline-check
• select
• multi-select

files

It allows you to get a value from a file input from the user.

import { files } from '@storybook/addon-knobs';

const label = 'Images';
const accept = '.xlsx, .pdf';
const defaultValue = [];
const groupId = 'GROUP-ID1';

const value = files(label, accept, defaultValue, groupId);

You can optionally specify a list of file types which the file input should accept. Multiple files can be selected, and will be returned as an array of Data URLs.

date

Allows you to get date (and time) from the user.

import { date } from '@storybook/addon-knobs';

const label = 'Event Date';
const defaultValue = new Date('Jan 20 2017');
const groupId = 'GROUP-ID1';

const value = date(label, defaultValue, groupId);

Note: the default value must not change - e.g., do not do date('Label', new Date()) or date('Label').

The date knob returns the selected date as stringified Unix timestamp (e.g. "1510913096516"). If your component needs the date in a different form you can wrap the date function:

function myDateKnob(name, defaultValue) {
  const stringTimestamp = date(name, defaultValue);
  return new Date(stringTimestamp);
}

button

It allows you to include a button and associated handler.

import { button } from '@storybook/addon-knobs';

const label = 'Do Something';
const handler = () => doSomething('foobar');
const groupId = 'GROUP-ID1';

button(label, handler, groupId);

Button knobs cause the story to re-render after the handler fires. You can prevent this by having the handler return false.

withKnobs options

withKnobs also accepts two optional options as story parameters. Usage:

import { withKnobs } from '@storybook/addon-knobs';

export default {
  title: 'Storybook Knobs',
  decorators: [withKnobs],
};

export const defaultView = () => <div />;
defaultView.parameters = {
  knobs: {
    // Doesn't emit events while user is typing.
    timestamps: true,

    // Escapes strings to be safe for inserting as innerHTML. This option is true by default. It's safe to set it to `false` with frameworks like React which do escaping on their side.
    // You can still set it to false, but it's strongly discouraged to set to true in cases when you host your storybook on some route of your main site or web app.
    escapeHTML: true,
  },
};

Typescript

If you are using Typescript, make sure you have the type definitions installed for the following libs:

• node
• react

You can install them using: (assuming you are using Typescript >2.0.)

yarn add @types/node @types/react --dev