94 lines
2.0 KiB
Markdown
94 lines
2.0 KiB
Markdown
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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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forumTopicId: 301473
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dashedName: add-classes-with-d3
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---
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# --description--
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Using a lot of inline styles on HTML elements gets hard to manage, even for smaller apps. It's easier to add a class to elements and style that class one time using CSS rules. D3 has the `attr()` method to add any HTML attribute to an element, including a class name.
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The `attr()` method works the same way that `style()` does. It takes comma-separated values, and can use a callback function. Here's an example to add a class of `container` to a selection:
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```js
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selection.attr("class", "container");
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```
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Note that the `class` parameter will remain the same whenever you need to add a class and only the `container` parameter will change.
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# --instructions--
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Add the `attr()` method to the code in the editor and put a class of `bar` on the `div` elements.
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# --hints--
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Your `div` elements should have a class of `bar`.
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```js
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assert($('div').attr('class').trim().split(/\s+/g).includes('bar'));
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```
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Your code should use the `attr()` method.
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```js
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assert(code.match(/\.attr/g));
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```
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# --seed--
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## --seed-contents--
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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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// 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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<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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```
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