Welcome to the Treehouse Community

The Treehouse Community is a meeting place for developers, designers, and programmers of all backgrounds and skill levels to get support. Collaborate here on code errors or bugs that you need feedback on, or asking for an extra set of eyes on your latest project. Join thousands of Treehouse students and alumni in the community today. (Note: Only Treehouse students can comment or ask questions, but non-students are welcome to browse our conversations.)

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and a supportive community. Start your free trial today.

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

enoch okyere
enoch okyere
4,681 Points

I am confused about how to add the "highlight" class to the previous sibling p tag. Any help?

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

list.addEventListener('click', function(e) {
  if (e.target.tagName == 'BUTTON') {

    if(e.target.tagName == 'P'){
      let prev = e.target.previousElementSibiling;
      prev.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

  if (e.target.tagName == 'BUTTON') {

    if(e.target.tagName == 'P'){
      let prev = e.target.previousElementSibiling;
      prev.className = "highlight";
    }
  }

If the tagName of e.target is 'BUTTON', then its tagName is not 'P'. Try deleting if(e.target.tagName == 'P'){ and the corresponding } and correcting the spelling of previousElementSibling.