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

Posted by Begana Choi
Begana Choi
Courses Plus Student 13,126 Points

why my code makes error? (add a class name)

here is my code and it says I have error that

There was an error with your code: TypeError: 'undefined' is not an object (evaluating 'p.className = 'highlight'')

and I have no idea why it's wrong.. please help meee thank you!!

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

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

KRIS NIKOLAISEN
KRIS NIKOLAISEN
54,972 Points

It is just previousElementSibling without the s at the end