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

Andres Braun
Andres Braun
3,130 Points
Posted by Andres Braun
Andres Braun
3,130 Points

I don`t know how to finish this exercise. Could you help me?

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

list.addEventListener('click', function(e) { if (e.target.tagName == 'BUTTON') { let button = e.target.parentNode; let p = button.previousElementSibling; p.className = 'highlight'; } });

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

list.addEventListener('click', function(e) {
  if (e.target.tagName == 'BUTTON') {
    let button = e.target.parentNode;
    let p = button.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>

2 Answers

KRIS NIKOLAISEN
KRIS NIKOLAISEN
54,968 Points

if (e.target.tagName == 'BUTTON') then e.target is the button. From there you just need the previousElementSibling of the button. You could shorten it as:

let p = e.target.previousElementSibling;
Andres Braun
Andres Braun
3,130 Points
Andres Braun
Andres Braun
3,130 Points

Thank you very much for your help!

Dmitry Polyakov
Dmitry Polyakov
4,989 Points
Dmitry Polyakov
Dmitry Polyakov
4,989 Points

The task is to add a class of 'highlight' to a button's immediate previous sibling which is a paragraph. The button that you click on is your e.target. First you need to save a reference to a button into a variable 'const button'. Then having a button saved in a variable it is easy to target its previous sibling with .previousElementSibling.

const button = e.target;

button.previousElementSibling.className = "highlight";

Andres Braun
Andres Braun
3,130 Points
Andres Braun
Andres Braun
3,130 Points

Thank you very much for your help!