Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

JavaScript JavaScript and the DOM (Retiring) Traversing the DOM Using previousElementSibling and insertBefore

Daniel McHugh
Daniel McHugh
1,821 Points
Posted by Daniel McHugh
Daniel McHugh
1,821 Points

Code no longer working after following the steps in this video and I'm not sure why.

I'm on the .previousElementSibling video and I tried to follow the code exactly, but it's not working. What's weirder is that the chrome console isn't saying there's anything wrong with the syntax so I'm confused. Help? 

const toggleList = document.getElementById('toggleList');
const listDiv = document.querySelector('.list');
const desctiptionInput = document.querySelector('input.description');
const desctiptionP = document.querySelector('p.description');
const descriptionButton = document.querySelector('button.description');
const listUL = listDiv.querySelector('ul');
const addItemInput = document.querySelector ('input.addItemInput'); 
const addItemButton = document.querySelector('button.addItemButton');




listUL.addEventListener('click', (event) => {
  if (event.target.tagName == 'BUTTON') {
    if (event.target.tagName == 'remove') {
      let li = event.target.parentNode;
      let ul = li.parentNode;
      ul.removeChild(li);
    }
    if (event.target.tagName == 'up') {
      let li = event.target.parentNode;
      let prevLi = li.previousElementSibling;
      let ul = li.parentNode;
      if (prevLi) {
      ul.insertBefore(li, prevLi);
      }
    }
  }
});

//document.addEventListener('click', (event) => {
//console.log(event.target);                          
//                          });

toggleList.addEventListener('click', () => {
  if (listDiv.style.display == 'none'){
    toggleList.textContent = 'Hide list';
    listDiv.style.display = 'block';
} else { 
  toggleList.textContent = 'Show list';
  listDiv.style.display = 'none';
}
                            });

descriptionButton.addEventListener('click', () => {
  descriptionP.innerHTML = DescriptionInput.value + ':';
  desctiptionInput.value = '';
                        });
addItemButton.addEventListener('click', () => {
  let ul = document.getElementsByTagName('ul')[0];
  let li = document.createElement('li');
  li.textContent = addItemInput.value; 
  ul.appendChild(li);
  addItemInput.value = '';


                               });
Daniel McHugh
Daniel McHugh
1,821 Points
Daniel McHugh
Daniel McHugh
1,821 Points

Here's the HTML

<!DOCTYPE html>
<html>
  <head>
    <title>JavaScript and the DOM</title>
    <link rel="stylesheet" href="css/style.css">
  </head>
  <body>
    <h1 id="myHeading">JavaScript and the DOM</h1>
    <p>Making a web page interactive</p>   
    <button id="toggleList">Hide list</button>
    <div class="list">
      <p class="description">Things that are purple:</p>
      <input type="text" class="description">
      <button class="description">Change list Description</button>
      <ul>
        <li>grapes
          <button class="up">Up</button>
          <button class="remove">Remove</button>
          </li>
        <li>amethyst
          <button class="up">Up</button>
          <button class="remove">Remove</button>
          </li>
        <li>lavender
          <button class="up">Up</button>
          <button class="remove">Remove</button>
          </li>
        <li>plums
          <button class="up">Up</button>
          <button class="remove">Remove</button>
          </li>
    </ul>
    <input type="text" class="addItemInput">
    <button class="addItemButton">Add item</button>
    </div>
    <script src="app.js"></script>
  </body>
</html>

2 Answers

Steven Parker
Steven Parker
231,236 Points
Steven Parker
Steven Parker
231,236 Points

Some of it is just simple spelling/capitalization errors:

  • "desctiptionInput" instead of "descriptionInput"
  • "DescriptionInput" instead of "descriptionInput"
  • "desctiptionP" instead of "descriptionP"

And some just looking in the wrong place (not a syntax error), like:

  • "(event.target.tagName == 'remove')" instead of "(event.target.className == 'remove')"
  • "(event.target.tagName == 'up')" instead of "(event.target.className == 'up')"
Daniel McHugh
Daniel McHugh
1,821 Points
Daniel McHugh
Daniel McHugh
1,821 Points

Thanks! Seems weird that the code seemed to still run as intended even with the spelling errors, but thanks for pointing them out. I must have made the misspelling often enough to make it sort of consistent.

Steven Parker
Steven Parker
231,236 Points
Steven Parker
Steven Parker
231,236 Points

Variable names are always your choice. So if you misspell something consistently throughout the program, it will work just as well as if it were spelled correctly.

Matt Brock
Matt Brock
28,330 Points
Matt Brock
Matt Brock
28,330 Points

Hey Daniel, you were using tagName instead of className in your eventListener function. Here's what it should be:

listUL.addEventListener('click', (event) => {
  if (event.target.tagName == 'BUTTON') {
    let li = event.target.parentNode;
    let ul = li.parentNode;

    if (event.target.className == 'remove') {
      ul.removeChild(li);
    }

    if (event.target.className == 'up') {
      let prevLi = li.previousElementSibling;
      if (prevLi) {
        ul.insertBefore(li, prevLi);
      }
    }
  }
});
Daniel McHugh
Daniel McHugh
1,821 Points
Daniel McHugh
Daniel McHugh
1,821 Points

Ah, makes sense. Thanks so much!

Matt Brock
Matt Brock
28,330 Points

You bet!