classnames

What is classnames?

The classnames package is a simple utility for conditionally joining class names together. It is commonly used in React projects but can be used anywhere that requires dynamic class name computation.

What are classnames's main functionalities?

String arguments

Combine multiple string arguments into one class name.

classnames('foo', 'bar'); // 'foo bar'

Object arguments

Use an object to include class names conditionally based on the truthiness of the object's values.

classnames({ 'foo': true, 'bar': false }); // 'foo'

Array arguments

Pass an array of class names which will be joined together.

classnames(['foo', 'bar']); // 'foo bar'

Mixed arguments

Combine string, object, and array arguments to form a class name string.

classnames('foo', { 'bar': true, 'duck': false }, ['baz', { 'quux': true }]); // 'foo bar baz quux'

Other packages similar to classnames

clsx

clsx is a tiny utility for constructing className strings conditionally. It is similar to classnames but is smaller and faster, making it a popular alternative.

emotion

Emotion is a performant and flexible CSS-in-JS library. While it is more than a class name utility, it provides similar functionalities in terms of composing and applying class names conditionally.

README

Classnames

A simple javascript utility for conditionally joining classNames together.

Install with npm or Bower.

npm install classnames

Use with node.js, browserify or webpack:

var classNames = require('classnames');
classNames('foo', 'bar'); // => 'foo bar'

Alternatively, you can simply include index.js on your page with a standalone <script> tag and it will export a global classNames method, or define the module if you are using RequireJS.

Changelog

Usage

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 of the key is falsy, it won't be included in the output.

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

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.

For example:

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

This version is slower (about 10x) so it is offered as an opt-in.

To use the dedupe version with node, browserify or webpack:

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

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

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.

License

(The MIT License)

Copyright (c) 2015 Jed Watson

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.