2018-09-30 22:01:58 +00:00
---
id: 587d7faa367417b2b2512bd4
title: Add a Hover Effect to a D3 Element
challengeType: 6
2019-08-05 16:17:33 +00:00
forumTopicId: 301469
2021-01-13 02:31:00 +00:00
dashedName: add-a-hover-effect-to-a-d3-element
2018-09-30 22:01:58 +00:00
---
2020-11-27 18:02:05 +00:00
# --description--
2018-09-30 22:01:58 +00:00
It's possible to add effects that highlight a bar when the user hovers over it with the mouse. So far, the styling for the rectangles is applied with the built-in D3 and SVG methods, but you can use CSS as well.
2020-11-27 18:02:05 +00:00
You set the CSS class on the SVG elements with the `attr()` method. Then the `:hover` pseudo-class for your new class holds the style rules for any hover effects.
2018-09-30 22:01:58 +00:00
2020-11-27 18:02:05 +00:00
# --instructions--
2018-09-30 22:01:58 +00:00
2020-11-27 18:02:05 +00:00
Use the `attr()` method to add a class of `bar` to all the `rect` elements. This changes the `fill` color of the bar to brown when you mouse over it.
2018-09-30 22:01:58 +00:00
2020-11-27 18:02:05 +00:00
# --hints--
2018-09-30 22:01:58 +00:00
2020-11-27 18:02:05 +00:00
Your `rect` elements should have a class of `bar` .
2018-09-30 22:01:58 +00:00
2020-11-27 18:02:05 +00:00
```js
assert($('rect').attr('class') == 'bar');
```
2018-09-30 22:01:58 +00:00
2020-11-27 18:02:05 +00:00
# --seed--
## --seed-contents--
2018-09-30 22:01:58 +00:00
```html
< style >
.bar:hover {
fill: brown;
}
< / style >
< body >
< script >
const dataset = [12, 31, 22, 17, 25, 18, 29, 14, 9];
2018-10-08 00:01:53 +00:00
2018-09-30 22:01:58 +00:00
const w = 500;
const h = 100;
2018-10-08 00:01:53 +00:00
2018-09-30 22:01:58 +00:00
const svg = d3.select("body")
.append("svg")
.attr("width", w)
.attr("height", h);
2018-10-08 00:01:53 +00:00
2018-09-30 22:01:58 +00:00
svg.selectAll("rect")
.data(dataset)
.enter()
.append("rect")
.attr("x", (d, i) => i * 30)
.attr("y", (d, i) => h - 3 * d)
.attr("width", 25)
.attr("height", (d, i) => 3 * d)
.attr("fill", "navy")
// Add your code below this line
2018-10-08 00:01:53 +00:00
2018-09-30 22:01:58 +00:00
// Add your code above this line
2018-10-08 00:01:53 +00:00
2018-09-30 22:01:58 +00:00
svg.selectAll("text")
.data(dataset)
.enter()
.append("text")
.text((d) => d)
.attr("x", (d, i) => i * 30)
.attr("y", (d, i) => h - (3 * d) - 3);
2018-10-08 00:01:53 +00:00
2018-09-30 22:01:58 +00:00
< / script >
< / body >
```
2020-11-27 18:02:05 +00:00
# --solutions--
2018-09-30 22:01:58 +00:00
2020-07-13 16:58:50 +00:00
```html
2019-06-20 16:49:47 +00:00
< style >
.bar:hover {
fill: brown;
}
< / style >
< body >
< script >
const dataset = [12, 31, 22, 17, 25, 18, 29, 14, 9];
const w = 500;
const h = 100;
const svg = d3.select("body")
.append("svg")
.attr("width", w)
.attr("height", h);
svg.selectAll("rect")
.data(dataset)
.enter()
.append("rect")
.attr("x", (d, i) => i * 30)
.attr("y", (d, i) => h - 3 * d)
.attr("width", 25)
.attr("height", (d, i) => 3 * d)
.attr("fill", "navy")
// Add your code below this line
.attr('class', 'bar')
// Add your code above this line
svg.selectAll("text")
.data(dataset)
.enter()
.append("text")
.text((d) => d)
.attr("x", (d, i) => i * 30)
.attr("y", (d, i) => h - (3 * d) - 3);
< / script >
< / body >
2018-09-30 22:01:58 +00:00
```
