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	id, title, challengeType, forumTopicId, dashedName
| id | title | challengeType | forumTopicId | dashedName | 
|---|---|---|---|---|
| 587d7fa7367417b2b2512bc8 | Add Classes with D3 | 6 | 301473 | add-classes-with-d3 | 
--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') == '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>