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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.
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.
Waiting: Your div elements should have a class of bar. Waiting: Your code should use the attr() method.