freeCodeCamp/guide/english/certifications/data-visualization/data-visualization-with-d3/add-a-hover-effect-to-a-d3-element/index.md

---
title: Add a Hover Effect to a D3 Element
---
## Add a Hover Effect to a D3 Element

### Hint 1

Add the ` bar ` class to all `rect ` elements.

### Hint 2

Use the ` attr() ` method to add attributes.

### Solution

Add the following line of code to the end of your ` rect ` methods chain:

```javascript
.attr("class","bar");
```