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

Justin Roberts
Justin Roberts
14,583 Points
Posted by Justin Roberts
Justin Roberts
14,583 Points

Not sure why this click handler isn't working for sibling

Not sure why this isn't working. When I go to preview it, it appears to meet the requirements of the directions. It's highlighting the sibling paragraphs, but it's giving me an error that one or more paragraphs aren't being highlighted.

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

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

Steven Parker
Steven Parker
229,657 Points
Steven Parker
Steven Parker
229,657 Points

Don't append to className.

At least not without checking to see if it is empty. It doesn't work correctly if the first character is a space.

For this challenge, it's sufficient to simply replace className. But when you want to add a class without affecting any that may already be there, use classList.add().

Justin Roberts
Justin Roberts
14,583 Points
Justin Roberts
Justin Roberts
14,583 Points

Yeah, ended up realizing shortly after posting this that the problem was the space before the class name. Was unaware of classList.add(), thanks for that!