--- id: 587d7fa7367417b2b2512bc8 title: Add Classes with D3 challengeType: 6 forumTopicId: 301473 dashedName: 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`. ```js assert($('div').attr('class') == 'bar'); ``` Your code should use the `attr()` method. ```js assert(code.match(/\.attr/g)); ``` # --seed-- ## --seed-contents-- ```html ``` # --solutions-- ```html ```