Classnames2

This is a fork of classnames package with es6 exports and other stuff.

Versions of this package should be remained the same as original classnames.

A simple JavaScript utility for conditionally joining classNames together.

Installation

Install with npm, Bower, or Yarn:

npm:

npm install classnames2 --save

Yarn (note that yarn add automatically saves the package to the dependencies in package.json):

yarn add classnames2

Usage

ES6 syntax

import classNames from 'classnames2';
classNames('foo', 'bar'); // => 'foo bar'

CommonJS

const classNames = require('classnames2/es6/common');
// or
const classNames = require('classnames2/es5/common');

AMD

define('module', ['classnames2/es5/umd'], function (classNames) {
  
});

The classNames function takes any number of arguments which can be a string or object. The argument 'foo' is short for { foo: true }. If the value associated with a given key is falsy, that key won't be included in the output.

classNames('foo', 'bar'); // => 'foo bar'
classNames('foo', { bar: true }); // => 'foo bar'
classNames({ 'foo-bar': true }); // => 'foo-bar'
classNames({ 'foo-bar': false }); // => ''
classNames({ foo: true }, { bar: true }); // => 'foo bar'
classNames({ foo: true, bar: true }); // => 'foo bar'

// lots of arguments of various types
classNames('foo', { bar: true, duck: false }, 'baz', { quux: true }); // => 'foo bar baz quux'

// other falsy values are just ignored
classNames(null, false, 'bar', undefined, 0, 1, { baz: null }, ''); // => 'bar 1'

Arrays will be recursively flattened as per the rules above:

var arr = ['b', { c: true, d: false }];
classNames('a', arr); // => 'a b c'

Dynamic class names with ES2015

If you're in an environment that supports computed keys (available in ES2015 and Babel) you can use dynamic class names:

let buttonType = 'primary';
classNames({ [`btn-${buttonType}`]: true });

Usage with React.js

This package is the official replacement for classSet, which was originally shipped in the React.js Addons bundle.

One of its primary use cases is to make dynamic and conditional className props simpler to work with (especially more so than conditional string manipulation). So where you may have the following code to generate a className prop for a <button> in React:

var Button = React.createClass({
  // ...
  render () {
    var btnClass = 'btn';
    if (this.state.isPressed) btnClass += ' btn-pressed';
    else if (this.state.isHovered) btnClass += ' btn-over';
    return <button className={btnClass}>{this.props.label}</button>;
  }
});

You can express the conditional classes more simply as an object:

var classNames = require('classnames');

var Button = React.createClass({
  // ...
  render () {
    var btnClass = classNames({
      btn: true,
      'btn-pressed': this.state.isPressed,
      'btn-over': !this.state.isPressed && this.state.isHovered
    });
    return <button className={btnClass}>{this.props.label}</button>;
  }
});

Because you can mix together object, array and string arguments, supporting optional className props is also simpler as only truthy arguments get included in the result:

var btnClass = classNames('btn', this.props.className, {
  'btn-pressed': this.state.isPressed,
  'btn-over': !this.state.isPressed && this.state.isHovered
});

Alternate dedupe version

There is an alternate version of classNames available which correctly dedupes classes and ensures that falsy classes specified in later arguments are excluded from the result set.

This version is slower (about 5x) so it is offered as an opt-in.

To use the dedupe version with Node.js, Browserify, or webpack:

var classNames = require('classnames/dedupe');

classNames('foo', 'foo', 'bar'); // => 'foo bar'
classNames('foo', { foo: false, bar: true }); // => 'bar'

For standalone (global / AMD) use, include dedupe.js in a <script> tag on your page.

Alternate bind version (for css-modules)

If you are using css-modules, or a similar approach to abstract class "names" and the real className values that are actually output to the DOM, you may want to use the bind variant.

Note that in ES2015 environments, it may be better to use the "dynamic class names" approach documented above.

var classNames = require('classnames/bind');

var styles = {
  foo: 'abc',
  bar: 'def',
  baz: 'xyz'
};

var cx = classNames.bind(styles);

var className = cx('foo', ['bar'], { baz: true }); // => "abc def xyz"

Real-world example:

/* components/submit-button.js */
import { Component } from 'react';
import classNames from 'classnames/bind';
import styles from './submit-button.css';

let cx = classNames.bind(styles);

export default class SubmitButton extends Component {
  render () {
    let text = this.props.store.submissionInProgress ? 'Processing...' : 'Submit';
    let className = cx({
      base: true,
      inProgress: this.props.store.submissionInProgress,
      error: this.props.store.errorOccurred,
      disabled: this.props.form.valid,
    });
    return <button className={className}>{text}</button>;
  }
};

Polyfills needed to support older browsers

classNames >=2.0.0

Array.isArray: see MDN for details about unsupported older browsers (e.g. <= IE8) and a simple polyfill.

Object.keys: see MDN for details about unsupported older browsers (e.g. <= IE8) and a simple polyfill. This is only used in dedupe.js.

License

MIT. Copyright (c) 2017 Jed Watson, Dmitry Zelenetskiy