react-bem-helper

React BEM helper

A helper making it easier to name React.js components according to BEM conventions. It removes the repetition from writing the component name multiple times for elements and elements with modifier classes on them.

Why?

I found myself writing code like this a lot in my React components:

<div className="c-componentName">
  <div className="c-componentName__inner">
    Some test
    <button className="c-componentName__button c-componentName__button--left">Button</button>
    <button className="c-componentName__button c-componentName__button--right">Button</button>
  </div>
</div>

Compare that to SCSS, where you might write components something like this:

.c-componentName {
  background: red;

  &__button {
    text-transform: uppercase;

    &--left { float: left; }
    &--right { float: right; }
  }
}

react-bem-helper allows you to write in a similar-ish DRY fashion, taking away some of the repetition and hopefully making it easier to scan.

How does it work?

A new helper instance is created with a an options object or a string representing the name of the component (componentName) in this example. The instantiated helper receives up to three arguments (element, modifiers, extra classes). When called, it generates a simple object with props that should be applied to the DOM element, for example { classNames: 'componentName' }. If you want, a prefix like c- can be automatically added by supplying an options object.

You can use the spread operator ({...object}) to apply the classes to the DOM element. Even though this is an ES6 feature, React compiles this to it's own ES5 compatible version.

Example

Here's how you would return the example HTML structure when using the helper.

var React     = require('react');
var BEMHelper = require('react-bem-helper');

module.exports = React.createClass({
  render: function() {
    var classes = new BEMHelper({
      name: 'componentName',
      prefix: 'c-'
    });

    return (
      <div {...classes()}>
        <div {...classes('inner')}>
          Some test
          <button {...classes('button', 'left')}>Button</button>
          <button {...classes('button', 'right')}>Button</button>
        </div>
      </div>
    );
  }
});

For optimization reasons, you might want to move new BEMHelper out of the render function. On occasions I've done something like this:

…
module.exports = React.createClass({
  bemHelper: new BEMHelper('componentName'),
  render: function() {
    var classes = this.bemHelper;
    return (
      <div {...classes()}>
      …
    )
  }
})

Usage

Installation

npm install react-bem-helper

Preparing the helper

Require the helper for your React component, and then instantiate a new instance of it, supplying an options object or a string representing the (block) name of the component.

var BEMhelper = require('react-bem-helper');

// Make 'componentName' the base name
var bemHelper = new BEMHelper('componentName')

// Or pass an options object with a prefix to be applied to all components
var bemHelper2 = new BEMHelper({
  name: 'componentName',
  prefix: 'mh-'
});

Using the helper

When executed, the helper returns an object with a className property. When the helper is called without any arguments, its value will consist of the block name and a prefix:

var React     = require('react'),
    BEMHelper = require('react-bem-helper');

module.exports = React.createClass({
  render: function() {
    var classes = new BEMHelper('componentName');

    return (
      <div {...classes('element', 'modifier', 'extra')} />
    );
    // Returns <div className='componentName__element componentName__element--modifier extra'/>
  }
});

The bemHelper supports up to three arguments: element, modifiers, and extra classes, although an object containing any of these parameters is also supported:

Alternate Syntax

var React     = require('react'),
    BEMHelper = require('react-bem-helper');

module.exports = React.createClass({
  render: function() {
    var classes = new BEMHelper('componentName');
    var options = {
      element:   'element',
      modifiers: 'modifier',
      extra:     'extra'
    };

    return (
      <div {...classes(options)} />
    );
    // Returns <div className='componentName__element componentName__element--modifier extra'/>
  }
});

Element

To generate a class like componentName__header, pass "header" as the first argument to the bemHelper:

var BEMHelper = require('react-bem-helper');
var bemHelper = new BEMHelper('componentName');

bemHelper('header'); // returns { className: 'componentName__header' }

The element argument only supports strings, but a configuration object replacing the element, modifiers and 'extra' paramers can be passed instead:

bemHelper({ element: 'header' }); // returns { className: 'componentName__header' }

Modifiers

Modifiers can be added as a String, Array, or Object. For every modifier an additional class is generated, based upon either the block name or element name:

var BEMHelper = require('react-bem-helper');
var bemHelper = new BEMHelper('componentName');

bemHelper(null, 'active');
// { className: 'componentName--active'}

bemHelper('lol', 'active');
// { className: 'componentName__lol--active'}

bemHelper('lol', ['active', 'funny']);
// { className: 'componentName__lol componentName__lol--active componentName__lol--funny'}

bemHelper('lol', {
  active: true,
  funny: false,
  playing: function() { return false;}
});
// { className: 'componentName__lol--active'}

If you pass an object as the modifiers argument, the helper will add the keys as classes for which their corresponding values are true. If a function is passed as a value, this function is executed.

If you're not using arguments, but a configuration object, add modifiers by adding a modifier or modifiers property to the configuration object:

bemHelper({ modifiers: 'active' }); // returns { className: 'componentName--active' }

As when using arguments, this syntax also supports arrays and objects as different ways of defining modifiers.

Extra classes

This argument allows you to do add extra classes to the element. Like the modifiers, extra classes can be added as a String, Array, or Object. The behaviour is the same, except that the classes are added as passed, and no prefix or block name is added.

var BEMHelper = require('react-bem-helper');
var bemHelper = new BEMHelper('componentName');

bemHelper('', '', ['one', 'two']);
// { className: 'componentName one two'}

bemHelper('', '', {
  active: true,
  funny: false,
  playing: function() { return false;}
});
// { className: 'componentName active'}

If you're not using arguments, but a configuration object, add extra classes by adding a extra property to the configuration object:

bemHelper({ extra: ['one', 'two'] }); // { className: 'componentName one two'}

As when using arguments, this syntax also supports arrays and objects as different ways of defining extra classes.

License

MIT License