freeCodeCamp/curriculum/challenges/english/04-data-visualization/data-visualization-with-d3/change-styles-based-on-data.md

---
id: 587d7fa7367417b2b2512bc7
title: Change Styles Based on Data
challengeType: 6
forumTopicId: 301479
dashedName: change-styles-based-on-data
---

# --description--

D3 is about visualization and presentation of data. It's likely you'll want to change the styling of elements based on the data. You can use a callback function in the `style()` method to change the styling for different elements.

For example, you may want to color a data point blue if it has a value less than 20, and red otherwise. You can use a callback function in the `style()` method and include the conditional logic. The callback function uses the `d` parameter to represent the data point:

```js
selection.style("color", (d) => {
  /* Logic that returns the color based on a condition */
});
```

The `style()` method is not limited to setting the `color` - it can be used with other CSS properties as well.

# --instructions--

Add the `style()` method to the code in the editor to set the `color` of the `h2` elements conditionally. Write the callback function so if the data value is less than 20, it returns "red", otherwise it returns "green".

**Note**  
You can use if-else logic, or the ternary operator.

# --hints--

The first `h2` should have a `color` of red.

```js
assert($('h2').eq(0).css('color') == 'rgb(255, 0, 0)');
```

The second `h2` should have a `color` of green.

```js
assert($('h2').eq(1).css('color') == 'rgb(0, 128, 0)');
```

The third `h2` should have a `color` of green.

```js
assert($('h2').eq(2).css('color') == 'rgb(0, 128, 0)');
```

The fourth `h2` should have a `color` of red.

```js
assert($('h2').eq(3).css('color') == 'rgb(255, 0, 0)');
```

The fifth `h2` should have a `color` of green.

```js
assert($('h2').eq(4).css('color') == 'rgb(0, 128, 0)');
```

The sixth `h2` should have a `color` of red.

```js
assert($('h2').eq(5).css('color') == 'rgb(255, 0, 0)');
```

The seventh `h2` should have a `color` of green.

```js
assert($('h2').eq(6).css('color') == 'rgb(0, 128, 0)');
```

The eighth `h2` should have a `color` of red.

```js
assert($('h2').eq(7).css('color') == 'rgb(255, 0, 0)');
```

The ninth `h2` should have a `color` of red.

```js
assert($('h2').eq(8).css('color') == 'rgb(255, 0, 0)');
```

# --seed--

## --seed-contents--

```html
<body>
  <script>
    const dataset = [12, 31, 22, 17, 25, 18, 29, 14, 9];

    d3.select("body").selectAll("h2")
      .data(dataset)
      .enter()
      .append("h2")
      .text((d) => (d + " USD"))
      // Add your code below this line


      // Add your code above this line
  </script>
</body>
```

# --solutions--

```html
<body>
  <script>
    const dataset = [12, 31, 22, 17, 25, 18, 29, 14, 9];

    d3.select("body").selectAll("h2")
      .data(dataset)
      .enter()
      .append("h2")
      .text((d) => (d + " USD"))
      .style("color", (d) => d < 20 ? "red" : "green")
  </script>
</body>
```
chore(curriculum): Remove files in wrong format 2018-10-04 14:37:37 +01:00			`---`
			`id: 587d7fa7367417b2b2512bc7`
			`title: Change Styles Based on Data`
			`challengeType: 6`
fix(curriculum): Added forumTopicId to remaining 1200 challeng… (#36558) 2019-08-05 09:17:33 -07:00			`forumTopicId: 301479`
feat(curriculum): restore seed + solution to Chinese (#40683) * feat(tools): add seed/solution restore script * chore(curriculum): remove empty sections' markers * chore(curriculum): add seed + solution to Chinese * chore: remove old formatter * fix: update getChallenges parse translated challenges separately, without reference to the source * chore(curriculum): add dashedName to English * chore(curriculum): add dashedName to Chinese * refactor: remove unused challenge property 'name' * fix: relax dashedName requirement * fix: stray tag Remove stray `pre` tag from challenge file. Signed-off-by: nhcarrigan <nhcarrigan@gmail.com> Co-authored-by: nhcarrigan <nhcarrigan@gmail.com> 2021-01-13 03:31:00 +01:00			`dashedName: change-styles-based-on-data`
chore(curriculum): Remove files in wrong format 2018-10-04 14:37:37 +01:00			`---`

Feat: add new Markdown parser (#39800) and change all the challenges to new `md` format. 2020-11-27 19:02:05 +01:00			`# --description--`

			D3 is about visualization and presentation of data. It's likely you'll want to change the styling of elements based on the data. You can use a callback function in the `style()` method to change the styling for different elements.

			For example, you may want to color a data point blue if it has a value less than 20, and red otherwise. You can use a callback function in the `style()` method and include the conditional logic. The callback function uses the `d` parameter to represent the data point:
fix(curriculum): Convert blockquote elements to triple backtick syntax for Data Visualization (#35995) * fix: convert data visualization * fix: reverted to blockquote * fix: changed js to json Co-Authored-By: Oliver Eyton-Williams <ojeytonwilliams@gmail.com> * fix: cleaned up code Co-Authored-By: Oliver Eyton-Williams <ojeytonwilliams@gmail.com> 2019-05-14 05:04:05 -07:00
			```js
			`selection.style("color", (d) => {`
			`/* Logic that returns the color based on a condition */`
			`});`
			```

Feat: add new Markdown parser (#39800) and change all the challenges to new `md` format. 2020-11-27 19:02:05 +01:00			The `style()` method is not limited to setting the `color` - it can be used with other CSS properties as well.

			`# --instructions--`

			Add the `style()` method to the code in the editor to set the `color` of the `h2` elements conditionally. Write the callback function so if the data value is less than 20, it returns "red", otherwise it returns "green".

			`Note`
			`You can use if-else logic, or the ternary operator.`

			`# --hints--`
chore(curriculum): Remove files in wrong format 2018-10-04 14:37:37 +01:00
Feat: add new Markdown parser (#39800) and change all the challenges to new `md` format. 2020-11-27 19:02:05 +01:00			The first `h2` should have a `color` of red.

			```js
			`assert($('h2').eq(0).css('color') == 'rgb(255, 0, 0)');`
chore(curriculum): Remove files in wrong format 2018-10-04 14:37:37 +01:00			```

Feat: add new Markdown parser (#39800) and change all the challenges to new `md` format. 2020-11-27 19:02:05 +01:00			The second `h2` should have a `color` of green.
chore(curriculum): Remove files in wrong format 2018-10-04 14:37:37 +01:00
Feat: add new Markdown parser (#39800) and change all the challenges to new `md` format. 2020-11-27 19:02:05 +01:00			```js
			`assert($('h2').eq(1).css('color') == 'rgb(0, 128, 0)');`
			```
chore(curriculum): Remove files in wrong format 2018-10-04 14:37:37 +01:00
Feat: add new Markdown parser (#39800) and change all the challenges to new `md` format. 2020-11-27 19:02:05 +01:00			The third `h2` should have a `color` of green.

			```js
			`assert($('h2').eq(2).css('color') == 'rgb(0, 128, 0)');`
			```

			The fourth `h2` should have a `color` of red.

			```js
			`assert($('h2').eq(3).css('color') == 'rgb(255, 0, 0)');`
			```

			The fifth `h2` should have a `color` of green.

			```js
			`assert($('h2').eq(4).css('color') == 'rgb(0, 128, 0)');`
			```

			The sixth `h2` should have a `color` of red.

			```js
			`assert($('h2').eq(5).css('color') == 'rgb(255, 0, 0)');`
			```

			The seventh `h2` should have a `color` of green.

			```js
			`assert($('h2').eq(6).css('color') == 'rgb(0, 128, 0)');`
			```

			The eighth `h2` should have a `color` of red.

			```js
			`assert($('h2').eq(7).css('color') == 'rgb(255, 0, 0)');`
			```

			The ninth `h2` should have a `color` of red.

			```js
			`assert($('h2').eq(8).css('color') == 'rgb(255, 0, 0)');`
			```

			`# --seed--`

			`## --seed-contents--`
chore(curriculum): Remove files in wrong format 2018-10-04 14:37:37 +01:00
			```html
			`<body>`
			`<script>`
			`const dataset = [12, 31, 22, 17, 25, 18, 29, 14, 9];`
fix(challenge-md): Fix quotes that failed in the transform 2018-10-08 01:01:53 +01:00
chore(curriculum): Remove files in wrong format 2018-10-04 14:37:37 +01:00			`d3.select("body").selectAll("h2")`
			`.data(dataset)`
			`.enter()`
			`.append("h2")`
			`.text((d) => (d + " USD"))`
			`// Add your code below this line`
fix(challenge-md): Fix quotes that failed in the transform 2018-10-08 01:01:53 +01:00


chore(curriculum): Remove files in wrong format 2018-10-04 14:37:37 +01:00			`// Add your code above this line`
			`</script>`
			`</body>`
			```

Feat: add new Markdown parser (#39800) and change all the challenges to new `md` format. 2020-11-27 19:02:05 +01:00			`# --solutions--`
chore(curriculum): Remove files in wrong format 2018-10-04 14:37:37 +01:00
Add solution d3challenges (#38222) * added solutions to data visualization with D3 * Update add-a-tooltip-to-a-d3-element.english.md * Update add-attributes-to-the-circle-elements.english.md * Update add-axes-to-a-visualization.english.md * Update add-document-elements-with-d3.english.md * Update add-inline-styling-to-elements.english.md * Update add-labels-to-scatter-plot-circles.english.md * Update change-styles-based-on-data.english.md * Update change-the-color-of-an-svg-element.english.md * Update change-the-presentation-of-a-bar-chart.english.md * Update create-a-bar-for-each-data-point-in-the-set.english.md * Update create-a-linear-scale-with-d3.english.md * Update create-a-scatterplot-with-svg-circles.english.md * Update display-shapes-with-svg.english.md * Update dynamically-change-the-height-of-each-bar.english.md * Update dynamically-set-the-coordinates-for-each-bar.english.md * Update invert-svg-elements.english.md * Update learn-about-svg-in-d3.english.md * Update select-a-group-of-elements-with-d3.english.md * Update set-a-domain-and-a-range-on-a-scale.english.md * Update style-d3-labels.english.md * Update work-with-dynamic-data-in-d3.english.md * Update use-a-pre-defined-scale-to-place-elements.english.md * Update use-dynamic-scales.english.md * Update use-the-d3.max-and-d3.min-functions-to-find-minimum-and-maximum-values-in-a-dataset.english.md * Update work-with-data-in-d3.english.md 2020-04-24 17:04:53 +05:30			```html
			`<body>`
			`<script>`
			`const dataset = [12, 31, 22, 17, 25, 18, 29, 14, 9];`

			`d3.select("body").selectAll("h2")`
			`.data(dataset)`
			`.enter()`
			`.append("h2")`
			`.text((d) => (d + " USD"))`
			`.style("color", (d) => d < 20 ? "red" : "green")`
			`</script>`
			`</body>`
chore(curriculum): Remove files in wrong format 2018-10-04 14:37:37 +01:00			```