var cx = require('bem-classnames');

cx(/* classes, [...props|className] */);

var classes = {
  name: 'button',
  modifiers: ['color', 'block'],
  states: ['disabled']
};

cx(classes, { color: 'green', block: true });  // "button button--green button--block"
cx(classes, { disabled: true });  // "button is-disabled"
cx(classes, 'a b', ['c', 'd']);  // "button a b c d"

// Default prefixes:
//
// cx.prefixes = {
//   modifiers: '{name}--',
//   states: 'is-'
// };

cx.prefixes.modifiers = '-';
cx(classes, { color: 'green' });  // "button -green"

// You can add the prefixes
cx.prefixes.foo = 'foo-';
classes.foo = ['a', 'b'];
cx(classes, { a: true, b: true });  // "button foo-a foo-b"

import React from 'react';
import cx from 'bem-classnames';

class Button extends React.Component {
  render() {
    let classes = {
      name: 'button',
      modifiers: ['color', 'size'],
      states: ['disabled']
    };

    return (
      <button className={cx(classes, this.props, this.props.className)}>
        {this.props.children}
      </button>
    );
  }
}

React.render(
  <Button color="green" size="xl" disabled={true} className="a b">Alo!</Button>,
  document.getElementById('example')
);

// "button button--green button--xl a b is-disabled"

class Button extends React.Component {
  render() {
    let classes = {
      button: {
        name: 'button',
        modifiers: ['color', 'size'],
        states: ['disabled']
      },
      button__inner: {
        name: 'button__inner',
        modifiers: ['align']
      }
    };

    return (
      <button className={cx(classes.button, this.props, this.props.className)}>
        <span className={cx(classes.button__inner, this.props)}>
          {this.props.children}
        </span>
      </button>
    );
  }
}

React.render(
  <Button color="green" align="center">Alo!</Button>,
  document.getElementById('example')
);

// button -> "button button--green"
// span -> "button__inner button__inner--center"