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--description--

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.

--instructions--

Add the attr() method to the code in the editor and put a class of bar on the div elements.

--hints--

Your div elements should have a class of bar.

assert($('div').attr('class').trim().split(/\s+/g).includes('bar'));

Your code should use the attr() method.

assert(code.match(/\.attr/g));

--seed--

--seed-contents--​

<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>

--solutions--

<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>