---
id: class-name-manipulation
title: Class Name Manipulation
permalink: class-name-manipulation.html
prev: two-way-binding-helpers.html
next: test-utils.html
---
`classSet()` is a neat utility for easily manipulating the DOM `class` string.
Here's a common scenario and its solution without `classSet()` :
```javascript
// inside some `<Message />` React component
render: function() {
var classString = 'message';
if (this.props.isImportant) {
classString += ' message-important';
}
if (this.props.isRead) {
classString += ' message-read';
}
// 'message message-important message-read'
return < div className = {classString} > Great, I'll be there.< / div > ;
}
```
This can quickly get tedious, as assigning class name strings can be hard to read and error-prone. `classSet()` solves this problem:
```javascript
render: function() {
var cx = React.addons.classSet;
var classes = cx({
'message': true,
'message-important': this.props.isImportant,
'message-read': this.props.isRead
});
// same final string, but much cleaner
return < div className = {classes} > Great, I'll be there.< / div > ;
}
```
When using `classSet()` , pass an object with keys of the CSS class names you might or might not need. Truthy values will result in the key being a part of the resulting string.
`classSet()` also lets pass class names in as arguments that are then concatenated for you:
```javascript
render: function() {
var cx = React.addons.classSet;
var importantModifier = 'message-important';
var readModifier = 'message-read';
var classes = cx('message', importantModifier, readModifier);
// Final string is 'message message-important message-read'
return < div className = {classes} > Great, I'll be there.< / div > ;
}
```
No more hacky string concatenations!
