92 lines
3.8 KiB
Markdown
92 lines
3.8 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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---
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## Description
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<section id='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 <code>style()</code> method to change the styling for different elements.
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For example, you may want to color a data point blue if has a value less than 20, and red otherwise. You can use a callback function in the <code>style()</code> method and include the conditional logic. The callback function uses the <code>d</code> parameter to represent the data point:
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```js
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selection.style("color", (d) => {
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/* Logic that returns the color based on a condition */
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});
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```
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The <code>style()</code> method is not limited to setting the <code>color</code> - it can be used with other CSS properties as well.
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</section>
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## Instructions
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<section id='instructions'>
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Add the <code>style()</code> method to the code in the editor to set the <code>color</code> of the <code>h2</code> 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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<strong>Note</strong><br>You can use if-else logic, or the ternary operator.
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</section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: The first <code>h2</code> should have a <code>color</code> of red.
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testString: assert($('h2').eq(0).css('color') == "rgb(255, 0, 0)", 'The first <code>h2</code> should have a <code>color</code> of red.');
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- text: The second <code>h2</code> should have a <code>color</code> of green.
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testString: assert($('h2').eq(1).css('color') == "rgb(0, 128, 0)", 'The second <code>h2</code> should have a <code>color</code> of green.');
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- text: The third <code>h2</code> should have a <code>color</code> of green.
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testString: assert($('h2').eq(2).css('color') == "rgb(0, 128, 0)", 'The third <code>h2</code> should have a <code>color</code> of green.');
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- text: The fourth <code>h2</code> should have a <code>color</code> of red.
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testString: assert($('h2').eq(3).css('color') == "rgb(255, 0, 0)", 'The fourth <code>h2</code> should have a <code>color</code> of red.');
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- text: The fifth <code>h2</code> should have a <code>color</code> of green.
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testString: assert($('h2').eq(4).css('color') == "rgb(0, 128, 0)", 'The fifth <code>h2</code> should have a <code>color</code> of green.');
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- text: The sixth <code>h2</code> should have a <code>color</code> of red.
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testString: assert($('h2').eq(5).css('color') == "rgb(255, 0, 0)", 'The sixth <code>h2</code> should have a <code>color</code> of red.');
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- text: The seventh <code>h2</code> should have a <code>color</code> of green.
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testString: assert($('h2').eq(6).css('color') == "rgb(0, 128, 0)", 'The seventh <code>h2</code> should have a <code>color</code> of green.');
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- text: The eighth <code>h2</code> should have a <code>color</code> of red.
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testString: assert($('h2').eq(7).css('color') == "rgb(255, 0, 0)", 'The eighth <code>h2</code> should have a <code>color</code> of red.');
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- text: The ninth <code>h2</code> should have a <code>color</code> of red.
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testString: assert($('h2').eq(8).css('color') == "rgb(255, 0, 0)", 'The ninth <code>h2</code> should have a <code>color</code> of red.');
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='html-seed'>
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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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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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// solution required
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```
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</section>
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