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JavaScript JavaScript and the DOM (Retiring) Making Changes to the DOM Appending Nodes

Christopher Flores
Christopher Flores
6,898 Points
Posted by Christopher Flores
Christopher Flores
6,898 Points

Need some fresh eyes right quick!

the console is telling me Uncaught TypeError: Cannot read property 'addEventListener' of null

Is this a typo error somewhere I'm not seeing? I can't add new list items until I fix this bug. I've skimmed through it but can't see the problem, pls hlp.

JAVASCRIPT code:

const toggleList = document.getElementById('toggleList'); const listDiv = document.querySelector('.list'); const descriptionInput = document.querySelector('input.description'); const descriptionP = document.querySelector('p.description'); const descriptionButton = document.querySelector('button.description'); const addItemInput = document.querySelector('input.addItemInput'); const addItemButton = document.querySelector('input.addItemButton');

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 + ':';
});

addItemButton.addEventListener('click', () => { let ul = document.getElementsByTagName('ul')[0]; let li = document.createElement('li'); li.textContent = addItemInput.value; ul.appendChild(li); });

HTML code:

<!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</li>
      <li>amethyst</li>
      <li>lavender</li>
      <li>plums</li>
    </ul>
  <input type="text" class="addItemInput">
  <button class="addItemButton">Add Item</button>
</div>
<script src="app.js"></script>

</body> </html>

Christopher Flores
Christopher Flores
6,898 Points
Christopher Flores
Christopher Flores
6,898 Points

Never mind guys I figured it out!

turns out, in the javascript section I forgot to switch the input.addItemButton to button.addItemButton, so later in the code the function and addEventListener couldn't sync up I suppose.

maybe this'll help others - the smallest thing can trip you up

1 Answer

Wiktor Bednarz
Wiktor Bednarz
18,647 Points
Wiktor Bednarz
Wiktor Bednarz
18,647 Points

Hey there Chris,

const addItemButton = document.querySelector('input.addItemButton');

here's your bug, I guess you meant to pass in ".addItemButton" query here or "button.addItemButton" following your calling scheme.