Welcome to Cosmos!

Cosmos is a visual design system and UI component collection. Its goal is to empower application developers in their pursuit to create engaging and rewarding user experiences.

Getting started

Using Cosmos in your app

The recommended approach for using Cosmos is individual component imports to bundle with a method of your choosing.

import ReactDOM from 'react-dom';
import { SomeComponent } from '@pega/cosmos-react-core';

ReactDOM.render(<SomeComponent {...props} />, el);

Developing Cosmos components

Cosmos adheres to the following code style guides:

• Javascript: https://github.com/airbnb/javascript
• CSS: https://github.com/airbnb/css
• React(Followed loosely at the moment): https://github.com/airbnb/javascript/tree/master/react

These are enforced by ESLint, Prettier and Stylelint with settings some overridden/ignored. If you feel a certain coding style is better suited this project or should be allowed please speak up and advocate. Shoot for consistency and cleanliness.

With that, please take a moment to setup Visual Studio Code. We require the following extensions to be installed:

• ESLint
• Prettier
• stylelint
• cspell
• styled-components

Cosmos will check the format of your code and fail builds on linting errors so best to have your workspace in sync as you go. Next...

Clone Cosmos:

$ git clone https://github.com/pegasystems/cosmos-react.git

Install node_modules:

$ npm i

Start Cosmos dev server to run Storybook:

$ npm run start:stories

Create your first component - Component names must capitalized, containing only letters:

$ npm run create:component name:YourComponent [type:fn(default)|class|ref] [test:false(default)|true]

This cmd will generate a directory at /packages/cosmos-core/components/YourComponent/ with the following files:

1. YourComponent.tsx - A React component populated with some basic boilerplate
2. YourComponent.stories.tsx - A file used for the Storybook documentation that will hold demo components
3. YourComponent.test.ts - An empty file to use for test code, optional
4. index.ts - An index file that will re-export the default export from your component file

Inside YourComponent.tsx will be some initial boilerplate:

import { forwardRef, FunctionComponent, PropsWithoutRef, Ref } from 'react';
import styled from 'styled-components';

import { BaseProps, ForwardProps, PropsWithDefaults } from '../../types';
import { defaultThemeProp } from '../../theme';

export interface YourComponentProps extends BaseProps {
  ref?: Ref<HTMLDivElement>;
}

type YourComponentPropsWithDefaults = PropsWithDefaults<YourComponentProps>;

const StyledYourComponent = styled.div<YourComponentPropsWithDefaults>``;

StyledYourComponent.defaultProps = defaultThemeProp;

const YourComponent: FunctionComponent<YourComponentProps & ForwardProps> = forwardRef(
  (props: PropsWithoutRef<YourComponentProps>, ref: Ref<HTMLDivElement>) => {
    return <StyledYourComponent ref={ref} {...props} />;
  }
);

export default YourComponent;

The YourComponent.stories.tsx file will provide a hot reloading dev environment in Storybook:

import YourComponent from './YourComponent';

// These are settings that storybook will use to render your component's stories
export default {
  title: 'Components/YourComponent',
  component: YourComponent
};

// This is the first story in your component's story book section
export const firstYourComponent = () => <YourComponent>Hello YourComponent</YourComponent>;