alfa-laboratory / cn-decorator

Best way to use BEM with React

cn decorator

NOW WE RECOMMEND TO USE bem-react-classname EVOLVED FROM cn decorator

Best way to use BEM with React

Features

• BEM methodology for React
• Themes management
• className proxy
• BEM overrides
• DI Components

BEM methodology for React

cn decorator provides simplest ability to generate BEM methodology classes inside React Component.

Basic example

import cn from 'cn-decorator';
import React from 'react';
import './my-component.css';

@cn('block-name')
class MyComponent extends React.Component {
    render(cn) {
        return <div className={ cn() } />;
    }
}

// Render result:
// <div class="block-name"></div>

Use for elements

import cn from 'cn-decorator';
import React from 'react';
import './my-component.css';

@cn('block-name')
class MyComponent extends React.Component {
    render(cn) {
        return (
            <div className={ cn() }>
                <span className={ cn('some-element') } />
            </div>
        );
    }
}

// Render result:
// <div class="block-name">
//     <span class="block-name__some-element"></span>
// </div>

Add mods

import cn from 'cn-decorator';
import React from 'react';
import './my-component.css';

@cn('block-name')
class MyComponent extends React.Component {
    render(cn) {
        return <div className={ cn({ mod1: true, mod2: 'value' }) } />;
    }
}

// Render result:
// <div class="block-name block-name_mod1 block-name_mod2_value"></div>

Mods for elements

import cn from 'cn-decorator';
import React from 'react';
import './my-component.css';

@cn('block-name')
class MyComponent extends React.Component {
    render(cn) {
        return (
            <div className={ cn() }>
                <span className={ cn('some-element', { mod1: true }) } />
            </div>
        );
    }
}

// Render result:
// <div class="block-name">
//     <span class="block-name__some-element block-name__some-element_mod1"></span>
// </div>

Themes management

cn decorator provides system for themes managements. You can setup your themes using cn.create factory. cn decorator uses first theme as default.

Basic example

// my-component.js
import cnDecorator from 'cn-decorator';
import React from 'react';
import './my-component.css';

const cn = cnDecorator.create(['on-color', 'on-white']);

@cn('block-name')
class MyComponent extends React.Component {
    render(cn) {
        return <div className={ cn() } />;
    }
}

// app.js
import React from 'react';
import MyComponent from './my-component';

class App extends React.Component {
    render() {
        return <MyComponent />;
    }
}

// Render result:
// <div class="block-name block-name_theme_on-color"></div>

Switch theme with public prop

// my-component.js
import cnDecorator from 'cn-decorator';
import React from 'react';
import './my-component.css';

const cn = cnDecorator.create(['on-color', 'on-white']);

@cn('block-name')
class MyComponent extends React.Component {
    render(cn) {
        return <div className={ cn() } />;
    }
}

// app.js
import React from 'react';
import MyComponent from './my-component';

class App extends React.Component {
    render() {
        return <MyComponent theme="on-white" />;
    }
}

// Render result:
// <div class="block-name block-name_theme_on-white"></div>

className proxy

cn decorator adds ability to React Component to proxy className prop.

Example

// my-component.js
import cn from 'cn-decorator';
import React from 'react';
import './my-component.css';

@cn('block-name')
class MyComponent extends React.Component {
    render(cn) {
        return <div className={ cn() } />;
    }
}

// app.js
import React from 'react';
import MyComponent from './my-component';

class App extends React.Component {
    render() {
        return <MyComponent className="custom-class" />;
    }
}

// Render result:
// <div class="block-name custom-class"></div>

BEM overrides

Using cn decorator you can easy seperate your logic from styles. Just use extends pattern to override base BEM block name. Use this feature to override component's styles.

// my-component.js
import cn from 'cn-decorator';
import React from 'react';
import './my-component.css';

@cn('block-name')
class MyComponent extends React.Component {
    render(cn) {
        return (
            <div className={ cn() }>
                <span className={ cn('some-element') } />
            </div>
        );
    }
}

// my-extended-component.js
import cn from 'cn-decorator';
import MyComponent from './my-component';
import './my-extended-component.css';

@cn('extended-block')
class MyExtendedComponent extends MyComponent {}

// Render result:
// <div class="extended-block">
//     <span class="extended-block__some-element"></span>
// </div>

DI Components

cn decorator includes dependency injection ability. It can help you to override default component's composition.

// my-component.js
import cn from 'cn-decorator';
import React from 'react';
import MyDepComponent from './my-dep-component';

@cn('block-name', MyDepComponent)
class MyComponent extends React.Component {
    render(cn, MyDepComponent) {
        return (
            <div className={ cn() }>
                <MyDepComponent />
            </div>
        );
    }
}

// Render result:
// <div class="block-name">
//     <div class="my-dep"></div>
// </div>

// my-overrided-component.js
import cn from 'cn-decorator';
import MyComponent from './my-component';
import MyOverDepComponent from './my-over-dep-component';

@cn('block-name', MyOverDepComponent)
class MyOverridedComponent extends MyComponent {}

// Render result:
// <div class="block-name">
//     <div class="my-over-dep"></div>
// </div>

Utils

Check with linters

npm run lint

Check with unit tests

npm run test

Benchmarks

npm run test-benchmark

License

The MIT License (MIT)

Copyright (c) 2017 Alfa Laboratory

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.

cn-decorator's Issues

access "cn" function not only in render method.

if render function in component was divided to multiple functions,
required manually add "cn" to each this function (which is not comfortable with map and reduce cases)

may be should somehow store cn in private method and have access to it via "this.cn()"

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CSS-specificity problems with `className` proxing

Setting external className for blocks isn't a safe way to overwrite CSS styles.
If we use only BEM-named classes it will have equal priority so that if there are same CSS properties browser will choose the last one found in the final CSS file.

AFAIK (but it is not exactly) bem-core bundler generate dependency graph so files with custom styles always go after default styles.

React developers usually use webpack with style-loader and css-loader for bundling with styles. In common case it doesn't guarantee correct order of compiled styles.

So the question is how did you fix this problem?
Maybe some special postCSS plugin for increasing specificity or something else?)

Не работает с React 16

Сегодня вышел, cn с ним не работает :-(