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 Johnny Kan
Johnny Kan
5,862 Points

Add class of highlight to element & sibling traversal. What is this challenge about? What are they asking?

I must have misunderstood the challenge. Here are the instructions: "The <ul> stored in the variable list has a click event listener that targets each <button> in the list. Complete the code to add a class of highlight to a <p> element that's an immediate previous sibling of the button being clicked."

I interpret it as setting the paragraph's class to 'highlight' when the Highlight-button is clicked. But apparently that's not it. Can anyone explain what this challenge is about? What am I supposed to do/what are they asking for?

Thanks in advance.

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

list.addEventListener('click', function(e) {
  if (e.target.tagName == 'BUTTON') {
    let p = e.target.previousElementSibling;
    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>
Johnny Kan
Johnny Kan
5,862 Points

Updated the code without <h1></h1>.

1 Answer

Clayton Perszyk
MOD
Clayton Perszyk
Treehouse Moderator 48,850 Points
Clayton Perszyk
Clayton Perszyk
Treehouse Moderator 48,850 Points

You don't need <h1>list</h1>. You are getting the list from the DOM with the document.getElementsByTagName('ul')[0];.

Otherwise, it should work.

Johnny Kan
Johnny Kan
5,862 Points

Oh sorry. The h1 was an early test I did, i.e. it should not be in my final code. But with or without the h1, I also believe it should work... so I guess I'm not the only one who doesn't understand what they are asking for in this challenge.