# Shakl

[![npm version](https://badge.fury.io/js/shakl.svg)](https://badge.fury.io/js/shakl) [![Build Status](https://travis-ci.org/sonaye/shakl.svg?branch=master)](https://travis-ci.org/sonaye/shakl)

<img src="shakl.svg" alt="Shakl logo" width="128">

## Features

- Exposes basic [primitives](#primitives) such as `View`, `Text` and `Touchable`,
- Supports static and [dynamic styles](#dynamic-styles) (based on props).
- Supports [theming](#theming): dynamic styles receive a `theme` prop from a `ThemeProvider`.
- Supports component extension using [`extend()`](#extending-styles) and [`attrs()`](#custom-props).
- Supports component composition using [`withComponent()`](#wrapping-another-component) and [`withChild()`](#wrapping-a-child).
- Uses regular inline styles under the hood (performance boost).
- Works [with React DOM](#usage-with-react-dom) too, same simple API, same benefits.
- No dependencies, all just React goodness.
- ~2 KB in size, with less than 100 lines of code.

### Benchmark

Time required to create a simple styled component (in ms).

<img src="benchmark/results.png" alt="Shakl Benchmark" width="600">

## Install

```bash
yarn add shakl
```

## Usage

### Creating a styled component

```js
import styled from 'shakl'

const Foo = styled(View)({ flex: 1 })

<Foo /> // <View style={{ flex: 1 }} />
```

### Primitives

By default, React Native's `View`, `Text`, and `TouchableOpacity` are exposed to you, they can be directly used.

```js
styled.View({ flex: 1 })
styled.Text({ color: 'blue' })
styled.Touchable({ padding: 10 })

// equivalent to
styled(View)({ flex: 1 })
styled(Text)({ color: 'blue' })
styled(TouchableOpacity)({ padding: 10 })
```

### Dynamic styles

```js
const Foo = styled.View((props) => ({ padding: props.padded ? 10 : 0 }))

<Foo /> // <View style={{ padding: 0 }} />
<Foo padded /> // <View style={{ padding: 10 }} />
```

### Theming

Mount a `ThemeProvider` and every dynamic style receives the theme through the `theme` prop.

```js
import styled, { ThemeProvider, useTheme } from 'shakl'

const theme = { primary: 'blue' }

const Title = styled.Text(({ theme }) => ({ color: theme.primary }))

const App = () => (
  <ThemeProvider theme={theme}>
    <Title>Hello</Title>
  </ThemeProvider>
)
```

- Function styles and function `attrs()` receive the theme, including components derived through `extend()`, `attrs()`, `withComponent()` and `withChild()`.
- An explicitly passed `theme` prop overrides the context value.
- The `theme` prop is never forwarded to the underlying component (the default `omitProps`).
- Static-styled components never subscribe to the context, so a theme change does not re-render them.
- Without a provider nothing changes: style functions receive their props exactly as before.
- `useTheme()` reads the theme from any component, and the raw `ThemeContext` is exported too.

### Extending styles

```js
const Title = styled.Text({ fontSize: 20 })
// <Text style={{ fontSize: 20 }} />

const BoldTitle = Title.extend({ fontWeight: 'bold' })
// <Text style={{ fontSize: 20, fontWeight: 'bold' }} />

const RedBoldTitle = BoldTitle.extend({ color: 'red' })
// <Text style={{ fontSize: 20, fontWeight: 'bold', color: 'red' }} />

const RedHeadline = styled(RedBoldTitle)({ fontSize: 28 }) // this works too
```

### Custom props

```js
const Foo = styled.Text({ color: 'blue' }).attrs({ numberOfLines: 1 })
// <Text style={{ color: 'blue' }} numberOfLines={1} />

// attrs({ .. }) only overwrites the `defaultProps` of the component
// for dynamic props however we can pass it a function

const MyText = styled.Text({ color: 'red' }).attrs((props) => ({
  numberOfLines: props.oneLiner ? 1 : 3
}))

// equivalent to
<MyText /> // <Text style={{ color: 'red }} numberOfLines={3} />
<MyText oneLiner /> // <Text style={{ color: 'red }} numberOfLines={1} />
```

### Wrapping another component

```js
const Button = styled(TouchableOpacity)({ flex: 1 })
const HighlightedButton = Button.withComponent(TouchableHighlight)

// equivalent to
const Button = (props) => <TouchableOpacity style={{ flex: 1 }} {...props} />

const HighlightedButton = (props) => (
  <TouchableHighlight style={{ flex: 1 }} {...props} />
)
```

### Wrapping a child

```js
const ButtonText = styled.Text({ color: 'blue' })
const Button = styled.Touchable({ flex: 1 }).withChild(ButtonText)

// equivalent to
const Button = ({ children, ...props }) => (
  <TouchableOpacity style={{ flex: 1 }} {...props}>
    <Text style={{ color: 'blue' }}>{children}</Text>
  </TouchableOpacity>
)

// to pass a ref to a child, use the `childRef` prop on the parent
// to pass custom props to a child, use `.withChild(Child, childProps)`
const CardText = styled.Text({ color: 'blue' })
const Card = styled.View({ flex: 1 }).withChild(CardText, { numberOfLines: 3 })

// equivalent to
const Card = ({ children, childRef, ...props }) => (
  <View style={{ flex: 1 }} {...props}>
    <Text ref={childRef} style={{ color: 'blue' }} numberOfLines={3}>
      {children}
    </Text>
  </View>
)

// you can also access parent props by passing a function `.withChild(Child, (parentProps) => childProps)`
const Card = styled.View({ flex: 1 }).withChild(CardText, (parentProps) => ({
  numberOfLines: parentProps.onLiner ? 1 : 3
}))

<Card />
// <View ..>
//   <Text ..>{children}</Text>
// </View>

<Card onLiner />
// <View ..>
//   <Text numberOfLines={1} ..>{children}</Text>
// </View>
```

### Using refs

```js
const List = styled(FlatList)({ flex: 1 })

<List ref={this.list} /> // based on React's forwardRef API (16.3.0)

// this.list.scrollTo({ y: 0 })
// or this.list.current.scrollTo({ y: 0 }) (with React.createRef)
```

### Using a custom display name for debugging

```js
styled(View, { name: 'YetAnotherView' })
```

Default display names are `styled(View)`, `styled(Text)`, `styled(Touchable)`, `styled(Component)`, etc.

### Using propTypes and defaultProps

```js
const Foo = styled.View({ flex: 1 })

Foo.propTypes = { .. }
Foo.defaultProps = { .. }
```

### Usage with React DOM

Shakl is internally decoupled from React Native and can be used in the DOM.

```js
import styled from 'shakl'

// no exposed primitives however, feel free to add your own
const styled.div = styled('div')

const Foo = styled.div({ background: '#eee' })

<Foo /> // <div style={{ background: '#eee' }} />
```

[![Edit shakl](https://codesandbox.io/static/img/play-codesandbox.svg)](https://codesandbox.io/s/52kw0jrn94?module=%2Fsrc%2FExample.js)

### Testing with Jest

Since Shakl supports both React Native and the DOM, we need to explicitly tell Jest that we are testing for React Native, otherwise it will test against the DOM by default, which causes exposed primitives to fail (`.. shakl.default.View is not a function ..` error).

```js
// add the follwing to your Jest configuration when testing for React Native
"moduleNameMapper": {
  "shakl": "<rootDir>/node_modules/shakl/lib/rn.js"
}
```