BEM class names generator

Friendly BEM class names generator. Great for React.

Bem-cn (aka BEM Class Name) is extra small (minified+gzipped less than 1.5Kb) and extremely simple client-side library and Node.js module.

Inspired by b_.

Justification

I spent a lot of time finding BEM class name generator, that meets my needs:

• Simple usage with React
• Support modifiers without value
• Mix multiple blocks
• Friendly chainable API

When my efforts had led to naught I've created this micro library.

Install

With Node.js:

npm i --save bem-cn

Or use Bower for install:

bower install --save bem-cn

Works with webpack and browserify:

// CommonJS
var block = require('bem-cn');

// or ES6 modules
import block from 'bem-cn';

Cheat sheet

var b = block('button');

// Block
b; // 'button'
b(); // 'button'

// Element
b('icon'); // 'button__icon'

// Modifier
b({type: 'text'});  // 'button button_type_text'
b({onlykey: true});  // 'button button_onlykey'
b({without: false});  // 'button'

b('icon', {name: 'check'}); // 'button__icon button__icon_name_check'
b('icon')({name: 'check'}); // 'button__icon button__icon_name_check'

// Mix another classes
b('icon').mix('another'); // 'button__icon another'
b('icon').mix(['one', 'two']); // 'button__icon one two'

// States like in SMACSS: https://smacss.com/book/type-state
b.state({hidden: true}); // 'button is-hidden'
b.state({hidden: false}); // 'button'
b.state({hidden: true, error: true}); // 'button is-hidden is-error'

// More states!
b.is({loading: true}); // 'button is-loading'
b.has({content: true}); // 'button has-content'

// Setup custom delimiters
block.setup({
    el: '~~',
    mod: '--',
    modValue: '-'
});

var b = block('block');

b('element'); // 'block~~element'
b({mod: 'value'}); // 'block block--mod-value'

// Setup namespace
block.setup({ns: 'ns-'});

var b = block('block');

b(); // 'ns-block'
b('element'); // 'ns-block__element'
b({mod: 'value'}); // 'ns-block ns-block_mod_value'

Try it with React

import block from 'bem-cn';
import React from 'react';
import ReactDOM from 'react-dom';

let b = block('popup');

let Popup = React.createClass({
    render() {
        let {skin, children} = this.props;

        return (
            <div className={b}>
            	<span className={b('icon')} />
            	<div className={b('content', {skin})}>
            		{children}
            	</div>
            </div>
        );
    }
});

ReactDOM.render(<Popup skin="bright">Hello!</Popup>, target);

/*
<div class="popup">
	<span class="popup__icon"></span>
	<div class="popup__content popup__content_skin_bright">
        Hello!
	</div>
</div>
 */

Troubleshooting

PropTypes warnings

bem-cn has specific chainable API. As a result, each call returns function for a further call. But most components are expecting property className as a string and using propTypes object for check this. In this case, you will see a warning. There are the couple of ways to avoid these warnings below.

#1

Use final call without arguments to get a string

<CustomComponent className={b('icon')()} />

#2

Use explicit call of method toString():

<CustomComponent className={b('icon').toString()} />

#3

Use less specific propTypes rules:

let CustomComponent = React.createClass({
    propTypes: {
        className: React.PropTypes.oneOf([
            React.PropTypes.string,
            React.PropTypes.func
        ])
    },
    // ...
});

ES3 browsers

bem-cn is fully compatible with ES5 browsers. If you are going to support ES3 browsers than just use es5 shim.