A simple JavaScript utility for conditionally joining classNames together.
Install with npm, Bower, or Yarn:
npm:
npm install classnames --save
Bower:
bower install classnames --save
Yarn (note that yarn add
automatically saves the package to the dependencies
in package.json
):
yarn add 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.
We take the stability and performance of this package seriously, because it is run millions of times a day in browsers all around the world. Updates are thoroughly reviewed for performance impacts before being released, and we have a comprehensive test suite.
Classnames follows the SemVer standard for versioning.
There is also a Changelog.
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'
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 });
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
});
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>;
}
};
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
.
MIT. Copyright (c) 2017 Jed Watson.