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


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## Hints

### Hint 1

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

### Hint 2

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


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## Solutions

<details><summary>Solution 1 (Click to Show/Hide)</summary>

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

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

</details>