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

Bruno Antonellini
Bruno Antonellini
7,168 Points
Posted by Bruno Antonellini
Bruno Antonellini
7,168 Points

I find this code challenge is kind of buggy. I've done it, it works, but i receive the "Bummer!" alert.

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

or this can easily be done with the following too:

ON LINE 5: e.target.previousElementSibling.className += " highlight";

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

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

Steven Parker
Steven Parker
231,261 Points
Steven Parker
Steven Parker
231,261 Points

Concatenating onto "className" is not a good way to add a class, especially if you don't know if the element has one already. If it doesn't, you'll be creating a spurious leading space, and you might be creating a duplicate if it does.

But this is a safe way to add a class without disturbing any that might be there already or risking a duplicate:

      p.classList.add('highlight');