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

Michaela Zajacova
Michaela Zajacova
4,165 Points

Can't add new <li> items on click - getting error

Hello everyone, I have checked my code and other questions in this section but still cant figure out why I cant add a new item to the list when I click on the button I keep getting "Uncaught TypeError: Cannot read property 'appendChild' of undefined at HTMLButtonElement.<anonymous>"

Below is my code - all other functions work: JS let myHeading = document.querySelector("h1");

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(".addItemInput"); const addItemButton = document.querySelector(".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 + ':'; descriptionInput.value = " ";


// this does not work addItemButton.addEventListener("click", () => { let ul = document.getElementsByTagName("ul")[0]; let li = document.createElement("li"); li.textContent = addItemInput.value; ul.appendChild(li); addItemInput.value = " "; });


<!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 the list</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>

Could anyone help please?

1 Answer

Lachlan Stevens
Lachlan Stevens
10,779 Points

To make it a little easier for others to help you, you can use the markdown syntax in the "Markdown Cheatsheet" to make the code a little human readable. For example, when pasting blocks of code, wrap your code with 3 backticks (```) on the line before and after. If you specify the language after the first set of backticks, that'll help us with syntax highlighting.

      <p>This is code!</p>

The specific problem you've highlighted appears to be because you haven't closed your button element here:

<button class="description">Change the list</button <ul>

Hope this helps!