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

Posted by rajdeepbrar
rajdeepbrar
3,006 Points

Practical Help

Why doesn't this work? This question is stumping me big time!

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

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

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

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

Steven Parker
Steven Parker
231,008 Points
Steven Parker
Steven Parker
231,008 Points

:point_right: You seem to be trying to target the wrong element.

The paragraph that you want to alter is the previous sibling of the button itself, but your code seems to be attempting to target the previous sibling of the button's parent.

Your code:

      let butt = e.target.parentNode;  // but the parent of the target is the <li>!

Corrected code:

      let butt = e.target;    // the event target *IS* the button
rajdeepbrar
rajdeepbrar
3,006 Points

I've tried so many things, I see what you are saying.

I just can't solve this, let me try something else and report back.

Steven Parker
Steven Parker
231,008 Points
Steven Parker
Steven Parker
231,008 Points

Just change the one line I show above.

rajdeepbrar
rajdeepbrar
3,006 Points

Thanks Steve!!

rajdeepbrar
rajdeepbrar
3,006 Points
rajdeepbrar
rajdeepbrar
3,006 Points

I've also tried this:

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

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

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

Steven Parker
Steven Parker
231,008 Points
Steven Parker
Steven Parker
231,008 Points

An event object (e) has no previousElementSibling property.