Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

JavaScript JavaScript and the DOM (Retiring) Traversing the DOM Sibling Traversal

Posted by benyoungblood
benyoungblood
10,062 Points

Cannot change className of parent node.

I am having issues getting the className for the preceding p element surrounding the button element to update its class name.

app.js 
const list = document.getElementsByTagName('ul')[0];

list.addEventListener('click', function(e) {
  if (e.target.tagName == 'BUTTON') {
      let button = e.target.parentNode;
      let prevElement = button.previousElementSibling;
      let p = button.parentNode;
        p.className = 'highlight';
  }
});
index.html 
<!DOCTYPE html>
<html>
    <head>
        <title>JavaScript and the DOM</title>
    </head>
    <link rel="stylesheet" href="style.css" />
    <body>
        <section>
            <h1>Making a Webpage Interactive</h1>
            <p>Things to Learn</p>
            <ul>
                <li><p>Element Selection</p><button>Highlight</button></li>
                <li><p>Events</p><button>Highlight</button></li>
                <li><p>Event Listening</p><button>Highlight</button></li>
                <li><p>DOM Traversal</p><button>Highlight</button></li>
            </ul>
        </section>
        <script src="app.js"></script>
    </body>
</html>

1 Answer

Emmanuel C
Emmanuel C
10,636 Points
Emmanuel C
Emmanuel C
10,636 Points

The parentNode of the e.target(button) is actually the li element. Then youre getting the previous sibling of the li element which would be another li unless you click the first one. You can just use the previousSibling on the e.target, that would get the preceding p element. Then change its class name to highlight.

if (e.target.tagName == 'BUTTON') {
    let button = e.target;
    let prevEl = button.previousSibling;
    prevEl.className = 'highlight';
}
benyoungblood
benyoungblood
10,062 Points

Thank you!