fela-plugin-extend/README.md

Fela plugin to extend style objects

# fela-plugin-extend

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Allows styles to be extended with other style objects. Supports a condition-based API.<br>
It automatically removes `null` and `undefined` values **before** merging styles.

## Installation

```sh
yarn add fela-plugin-extend
```

You may alternatively use `npm i --save fela-plugin-extend`.

## Usage

Make sure to read the documentation on [how to use plugins](https://fela.js.org/docs/latest/advanced/plugins#using-plugins).

```javascript
import { createRenderer } from 'fela'
import extend from 'fela-plugin-extend'

const renderer = createRenderer({
  plugins: [extend()],
})
```

## Example

### `extend: styleObject`

#### Input

```javascript
{
  color: 'red',
  extend: { backgroundColor: 'blue' }
}
```

#### Output

```javascript
{
  color: 'red',
  backgroundColor: 'blue'
}
```

### `extend: { condition, styleObject }`

#### Input

```javascript
{
  color: 'red',
  extend: {
    condition: props.bg === true,
    style: { backgroundColor: 'blue' }
  }
}
```

#### Output

Rendered using `{ bg: true }` as `props`:

```javascript
{
  color: 'red',
  backgroundColor: 'blue'
}
```

Rendered using `{ bg: false }` as `props`

```javascript
{
  color: 'red'
}
```

### `extend: [...]`

You can also mix basic and conditional extending.
It will extend the styles from left to right.

```javascript
{
  color: 'red',
  extend: [{
    fontSize: '12px',
    lineHeight: 1.5
  }, {
    condition: props.bg === true,
    style: { backgroundColor: 'blue' }
  }, {
    lineHeight: 1.2
  }]
}
```

#### Output

Using `{ bg: true }` as `props`:

```javascript
{
  color: 'red',
  fontSize: '12px',
  lineHeight: 1.2,
  backgroundColor: 'blue'
}
```

## License

Fela is licensed under the [MIT License](http://opensource.org/licenses/MIT).<br>
Documentation is licensed under [Creative Commons License](http://creativecommons.org/licenses/by/4.0/).<br>
Created with ♥ by [@robinweser](http://weser.io) and all the great contributors.