2018-10-10 18:03:03 -04:00
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---
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id: 587d7fa7367417b2b2512bc8
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title: Add Classes with D3
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challengeType: 6
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2020-09-18 00:13:05 +08:00
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forumTopicId: 301473
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localeTitle: 用 D3 添加 Class
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2018-10-10 18:03:03 -04:00
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---
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## Description
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2020-09-18 00:13:05 +08:00
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<section id='description'>
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即使对小型 app 来说在 HTML 元素中大量使用内联样式表也十分难以管理。更方便的是给元素添加遵守 CSS 规则的类。D3 中的 <code>attr()</code> 方法可以给元素添加任何 HTML 属性，包括类名称。
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<code>attr()</code> 方法和 <code>style()</code> 的使用方法一样。它以逗号分隔的键值对为参数使用回调函数。这里是一个给选中元素添加类名为 "container" 的例子：<code>selection.attr("class", "container");</code>
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注意当 "container" 元素改变或者添加一个 class 时，"class" 参数会保持不变。
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</section>
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2018-10-10 18:03:03 -04:00
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## Instructions
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2020-09-18 00:13:05 +08:00
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<section id='instructions'>
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在编辑器中添加 <code>attr()</code> 方法，给 <code>div</code> 元素添加类名 <code>bar</code>。
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</section>
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2018-10-10 18:03:03 -04:00
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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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2020-09-18 00:13:05 +08:00
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- text: 你的 <code>div</code>元素应该有一个<code>bar</code> 类。
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2020-02-18 01:40:55 +09:00
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testString: assert($('div').attr('class') == "bar");
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2020-09-18 00:13:05 +08:00
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- text: 你应该使用 <code>attr()</code> 方法。
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2020-02-18 01:40:55 +09:00
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testString: assert(code.match(/\.attr/g));
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2018-10-10 18:03:03 -04:00
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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 {
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width: 25px;
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height: 100px;
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display: inline-block;
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background-color: blue;
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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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d3.select("body").selectAll("div")
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.data(dataset)
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.enter()
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.append("div")
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2020-09-18 00:13:05 +08:00
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// 在下面添加你的代码
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2018-10-10 18:03:03 -04:00
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2020-09-18 00:13:05 +08:00
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// 在上面添加你的代码
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2018-10-10 18:03:03 -04:00
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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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2020-09-18 00:13:05 +08:00
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```html
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<style>
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.bar {
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width: 25px;
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height: 100px;
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display: inline-block;
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background-color: blue;
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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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d3.select("body").selectAll("div")
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.data(dataset)
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.enter()
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.append("div")
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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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</script>
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</body>
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2018-10-10 18:03:03 -04:00
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```
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2020-08-13 17:24:35 +02:00
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2020-09-18 00:13:05 +08:00
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</section>
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