curriculum/challenges/english/blocks/data-visualization-with-d3/587d7fa7367417b2b2512bc8.md
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.
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:
selection.attr('class', 'container');
Note that the class parameter will remain the same whenever you need to add a class and only the container parameter will change.
Add the attr() method to the code in the editor and put a class of bar on the div elements.
Your div elements should have a class of bar.
assert.isTrue(document.querySelector('div')?.classList.contains('bar'));
Your code should use the attr() method.
assert.match(code, /\.attr/g);
<style>
.bar {
width: 25px;
height: 100px;
display: inline-block;
background-color: blue;
}
</style>
<body>
<script>
const dataset = [12, 31, 22, 17, 25, 18, 29, 14, 9];
d3.select('body')?.selectAll('div').data(dataset).enter().append('div');
// Add your code below this line
// Add your code above this line
</script>
</body>
<style>
.bar {
width: 25px;
height: 100px;
display: inline-block;
background-color: blue;
}
</style>
<body>
<script>
const dataset = [12, 31, 22, 17, 25, 18, 29, 14, 9];
d3.select('body')
.selectAll('div')
.data(dataset)
.enter()
.append('div')
// Add your code below this line
.attr('class', 'bar');
// Add your code above this line
</script>
</body>