124 lines
2.8 KiB
Markdown
124 lines
2.8 KiB
Markdown
---
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id: 587d7fa7367417b2b2512bc7
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title: Change Styles Based on Data
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challengeType: 6
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forumTopicId: 301479
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dashedName: change-styles-based-on-data
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---
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# --description--
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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.
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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:
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```js
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selection.style("color", (d) => {
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});
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```
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The `style()` method is not limited to setting the `color` - it can be used with other CSS properties as well.
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# --instructions--
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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.
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**Note:** You can use if-else logic, or the ternary operator.
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# --hints--
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The first `h2` should have a `color` of red.
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```js
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assert($('h2').eq(0).css('color') == 'rgb(255, 0, 0)');
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```
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The second `h2` should have a `color` of green.
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```js
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assert($('h2').eq(1).css('color') == 'rgb(0, 128, 0)');
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```
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The third `h2` should have a `color` of green.
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```js
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assert($('h2').eq(2).css('color') == 'rgb(0, 128, 0)');
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```
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The fourth `h2` should have a `color` of red.
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```js
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assert($('h2').eq(3).css('color') == 'rgb(255, 0, 0)');
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```
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The fifth `h2` should have a `color` of green.
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```js
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assert($('h2').eq(4).css('color') == 'rgb(0, 128, 0)');
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```
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The sixth `h2` should have a `color` of red.
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```js
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assert($('h2').eq(5).css('color') == 'rgb(255, 0, 0)');
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```
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The seventh `h2` should have a `color` of green.
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```js
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assert($('h2').eq(6).css('color') == 'rgb(0, 128, 0)');
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```
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The eighth `h2` should have a `color` of red.
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```js
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assert($('h2').eq(7).css('color') == 'rgb(255, 0, 0)');
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```
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The ninth `h2` should have a `color` of red.
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```js
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assert($('h2').eq(8).css('color') == 'rgb(255, 0, 0)');
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```
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# --seed--
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## --seed-contents--
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```html
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<body>
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<script>
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const dataset = [12, 31, 22, 17, 25, 18, 29, 14, 9];
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d3.select("body").selectAll("h2")
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.data(dataset)
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.enter()
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.append("h2")
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.text((d) => (d + " USD"))
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// Add your code below this line
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// Add your code above this line
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</script>
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</body>
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```
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# --solutions--
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```html
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<body>
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<script>
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const dataset = [12, 31, 22, 17, 25, 18, 29, 14, 9];
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d3.select("body").selectAll("h2")
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.data(dataset)
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.enter()
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.append("h2")
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.text((d) => (d + " USD"))
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.style("color", (d) => d < 20 ? "red" : "green")
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</script>
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</body>
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```
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