133 lines
2.9 KiB
Markdown
133 lines
2.9 KiB
Markdown
---
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id: 587d7faa367417b2b2512bd4
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title: Add a Hover Effect to a D3 Element
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challengeType: 6
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forumTopicId: 301469
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---
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## Description
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<section id='description'>
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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.
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You set the CSS class on the SVG elements with the <code>attr()</code> method. Then the <code>:hover</code> pseudo-class for your new class holds the style rules for any hover effects.
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</section>
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## Instructions
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<section id='instructions'>
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Use the <code>attr()</code> method to add a class of <code>bar</code> to all the <code>rect</code> elements. This changes the <code>fill</code> color of the bar to brown when you mouse over it.
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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: Your <code>rect</code> elements should have a class of <code>bar</code>.
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testString: assert($('rect').attr('class') == "bar");
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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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<style>
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.bar:hover {
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fill: brown;
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}
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</style>
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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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const w = 500;
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const h = 100;
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const svg = d3.select("body")
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.append("svg")
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.attr("width", w)
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.attr("height", h);
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svg.selectAll("rect")
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.data(dataset)
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.enter()
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.append("rect")
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.attr("x", (d, i) => i * 30)
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.attr("y", (d, i) => h - 3 * d)
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.attr("width", 25)
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.attr("height", (d, i) => 3 * d)
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.attr("fill", "navy")
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// Add your code below this line
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// Add your code above this line
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svg.selectAll("text")
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.data(dataset)
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.enter()
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.append("text")
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.text((d) => d)
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.attr("x", (d, i) => i * 30)
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.attr("y", (d, i) => h - (3 * d) - 3);
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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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<style>
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.bar:hover {
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fill: brown;
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}
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</style>
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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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const w = 500;
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const h = 100;
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const svg = d3.select("body")
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.append("svg")
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.attr("width", w)
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.attr("height", h);
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svg.selectAll("rect")
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.data(dataset)
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.enter()
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.append("rect")
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.attr("x", (d, i) => i * 30)
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.attr("y", (d, i) => h - 3 * d)
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.attr("width", 25)
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.attr("height", (d, i) => 3 * d)
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.attr("fill", "navy")
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// Add your code below this line
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.attr('class', 'bar')
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// Add your code above this line
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svg.selectAll("text")
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.data(dataset)
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.enter()
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.append("text")
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.text((d) => d)
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.attr("x", (d, i) => i * 30)
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.attr("y", (d, i) => h - (3 * d) - 3);
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</script>
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</body>
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```
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</section>
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