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 DOM Scripting By Example Editing and Filtering Names Filter Invitees Who Have Not Responded

Dennis Terrey
Dennis Terrey
2,527 Points
Posted by Dennis Terrey
Dennis Terrey
2,527 Points

Uncaught TypeError: Cannot read property 'insertBefore' of null at app.js:13

This is driving me insane, can't for the life figure out what the issue is. Any help would be greatly appreciated!

const form = document.getElementById('registrar');
const input = form.querySelector('input');
const mainDiv = form.querySelector('.main');
const ul = document.getElementById('invitedList');
const div = document.createElement('div');
const filterLabel = document.createElement('label');
const filterCheckBox = document.createElement('input');

filterLabel.textContent = "Hide those who haven't responded";
filterCheckBox.type = 'checkbox';
div.appendChild(filterLabel);
div.appendChild(filterCheckBox);
mainDiv.insertBefore(div, ul);

function createLI(text) {
    const li = document.createElement('li');
    const label = document.createElement('label');
    const checkbox = document.createElement('input');
    const span = document.createElement('span');
    const editButton = document.createElement('button');
    const removeButton = document.createElement('button');
    span.textContent = text;
    li.appendChild(span);
    label.textContent = 'Confirmed';
    checkbox.type = 'checkbox';
    label.appendChild(checkbox);
    li.appendChild(label);
    editButton.textContent = 'edit';
    li.appendChild(editButton);
    removeButton.textContent = 'remove';
    li.appendChild(removeButton);
    return li;
}

form.addEventListener('submit', (e) => {
    const text = input.value;
    const li = createLI(text);
    e.preventDefault();
    input.value = '';
    ul.appendChild(li);
});

ul.addEventListener('change', (e) => {
    const checkbox = event.target;
    const checked = checkbox.checked;
    const listItem = checkbox.parentNode.parentNode;
    if (checked) {
        listItem.className = 'responded';
    } else {
        listItem.className = ''
    }
});

ul.addEventListener('click', (e) => {
    if (e.target.tagName === 'BUTTON') {
        const button = e.target;
        const li = button.parentNode;
        const ul = li.parentNode;
        if(button.textContent === 'remove') {
            ul.removeChild(li);
        } else if (button.textContent === 'edit') {
            const span = li.firstElementChild;
            const input = document.createElement('input');
            input.type = 'text';
            input.value = span.textContent;
            li.insertBefore(input, span);
            li.removeChild(span);
            button.textContent = 'save';
        } else if (button.textContent === 'save') {
            const input = li.firstElementChild;
            const span = document.createElement('span');
            span.textContent = input.value;
            li.insertBefore(span, input);
            li.removeChild(input);
            button.textContent = 'save';
        }
    }
});
Steve Hunter
Steve Hunter
57,712 Points

It looks like mainDiv contains null so the assignment of form.querySelector('.main'); hasn't worked. Is main the correct class name?

Steve.

Dennis Terrey
Dennis Terrey
2,527 Points
Dennis Terrey
Dennis Terrey
2,527 Points

Steve Hunter thanks for the help! I should have really posted the HTML.

<!DOCTYPE html>
<html>
<head>
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>RSVP App</title>
  <link href="https://fonts.googleapis.com/css?family=Courgette" rel="stylesheet">
  <link href="https://fonts.googleapis.com/css?family=Lato:400,700" rel="stylesheet">
  <link href="css/style.css" rel="stylesheet">
</head>
<body>
  <div class="wrapper">
    <header>
      <h1>RSVP</h1>
      <p>A Treehouse App test</p>
      <form id="registrar">
        <input type="text" name="name" placeholder="Invite Someone">
        <button type="submit" name="submit" value="submit">Submit</button>
      </form>
    </header>

    <div class="main">  
      <h2>Invitees</h2>
      <ul id="invitedList"></ul>    
    </div>
  </div>
  <script type="text/javascript" src="js/app.js"></script>
</body>
</html>

3 Answers

Steven Parker
Steven Parker
231,248 Points
Steven Parker
Steven Parker
231,248 Points

Your selection starts at the wrong point in the DOM tree.

I do know a bit about JavaScript, and Steve is correct that since there is no element with class main inside the form with id "registrar", then mainDiv will be null.

But since the class main is unique on the page, you don't need a child selector and can get the correct value this way:

const mainDiv = document.querySelector('.main');

Also, on the last line of code, I think you may have meant to write "edit" instead of "save":

            button.textContent = 'edit';
Steve Hunter
Steve Hunter
57,712 Points

Woohoo! I got something right in JS! :smile:

Steve Hunter
Steve Hunter
57,712 Points
Steve Hunter
Steve Hunter
57,712 Points

Hi Dennis,

Should it be form.querySelector(".main") or rather document.querySelector(".main")? The main class isn't inside the form, so use the document? (I'm not a JS expert, I'm afraid!)

And perhaps try document.querySelector("div > .main")

Just some thoughts.

Steve.

Dennis Terrey
Dennis Terrey
2,527 Points
Dennis Terrey
Dennis Terrey
2,527 Points

Thank you Steve Hunter & Steven Parker that did the trick! Really appreciate the help!

Steve Hunter
Steve Hunter
57,712 Points

No problem! :+1: :smile: