Pen Settings

HTML

CSS

CSS Base

Vendor Prefixing

Add External Stylesheets/Pens

Any URL's added here will be added as <link>s in order, and before the CSS in the editor. If you link to another Pen, it will include the CSS from that Pen. If the preprocessor matches, it will attempt to combine them before processing.

+ add another resource

JavaScript

Babel includes JSX processing.

Add External Scripts/Pens

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor. You can use the URL of any other Pen and it will include the JavaScript from that Pen.

+ add another resource

Packages

Add Packages

Search for and use JavaScript packages from npm here. By selecting a package, an import statement will be added to the top of the JavaScript editor for this package.

Behavior

Save Automatically?

If active, Pens will autosave every 30 seconds after being saved once.

Auto-Updating Preview

If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.

Format on Save

If enabled, your code will be formatted when you actively save your Pen. Note: your code becomes un-folded during formatting.

Editor Settings

Code Indentation

Want to change your Syntax Highlighting theme, Fonts and more?

Visit your global Editor Settings.

HTML

              
                <section class="centered">
  <h1>500 Server Error</h1>
  <div class="container">
    <span class="message" id="js-whoops"></span> <span class="message" id="js-appears"></span> <span class="message" id="js-error"></span> <span class="message" id="js-apology"></span>
    <div><span class="hidden" id="js-hidden">Message Here</span></div>
  </div>
</section>
              
            
!

CSS

              
                @import url('https://fonts.googleapis.com/css?family=Lato|Roboto+Slab');

* {
  position: relative;
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

.centered {
  height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
}

h1 {
  margin-bottom: 50px;
  font-family: 'Lato', sans-serif;
  font-size: 50px;
}

.message {
  display: inline-block;
  line-height: 1.2;
  transition: line-height .2s, width .2s;
  overflow: hidden;
}

.message,
.hidden {
  font-family: 'Roboto Slab', serif;
  font-size: 18px;
}

.hidden {
  color: #FFF;
}
              
            
!

JS

              
                // Here are the different messages we'll use for creating the 500 displayable message
const messages = [
  ['Whoops.', 'Oops.', 'Excuse me.', 'Oh Dear.', 'Well poo.', 'Hm...', 'This is awkward.', 'Well gosh!'],
  ['It appears', 'Looks like', 'Unfortunately,', 'It just so happens', 'Sadly,', 'Seemingly from nowhere'],
  ['there was an error.', 'we goofed up.', 'a bad thing happend.', 'the server crashed.', 'a bug appeared.', 'someone did a naughty.', 'pixies got into the server!', 'the server threw a tantrum.', 'the website had a bad day.', 'our code pooped out.'],
  ['Sorry.', 'Apologies.', 'Our bad.', 'Sad day.', 'We are quite contrite.', 'Beg pardon.']
];

// These are the different elements we'll be populating. They are in the same order as the messages array
const messageElements = [
  document.querySelector('#js-whoops'),
  document.querySelector('#js-appears'),
  document.querySelector('#js-error'),
  document.querySelector('#js-apology')
];

// we'll use this element for width calculations
const widthElement = document.querySelector('#js-hidden');
// keeping track of the message we just displayed last
let lastMessageType = -1;
// How often the page should swap messages
let messageTimer = 4000;

// on document load, setup the initial messages AND set a timer for setting messages
document.addEventListener('DOMContentLoaded', (event) => {
  setupMessages();
  setInterval(() => {
    swapMessage();
  }, messageTimer);
});

// Get initial messages for each message element
function setupMessages() {
  messageElements.forEach((element, index) => {
    let newMessage = getNewMessage(index);
    element.innerText = newMessage;
  });
}

// set the width of a given element to match its text's width
function calculateWidth(element, message) {
  // use our dummy hidden element to get the text's width. Then use that to set the real element's width
  widthElement.innerText = message;
  let newWidth = widthElement.getBoundingClientRect().width;
  element.style.width = `${newWidth}px`;
}

// swap a message for one of the message types
function swapMessage() {
  let toSwapIndex = getNewSwapIndex();
  let newMessage  = getNewMessage(toSwapIndex);
  // Animate the disappearing, setting width, and reappearing
  messageElements[toSwapIndex].style.lineHeight = '0';
  // once line height is done transitioning, set element width & message
  setTimeout(() => {
    // make sure the element has a width set for transitions
    checkWidthSet(toSwapIndex, messageElements[toSwapIndex].innerText);
    // set the new text
    messageElements[toSwapIndex].innerText = newMessage; 
    // set the new width
    calculateWidth(messageElements[toSwapIndex], newMessage);
  }, 200);
  // once width is done, transition the lineheight back to 1 so we can view the message
  setTimeout(() => {
    messageElements[toSwapIndex].style.lineHeight = '1.2';
  }, 400);
}

// We need to make sure that the element at the passed index has a width set so we can use transitions
function checkWidthSet(index, message) {
  if (false == messageElements[index].style.width) {
    messageElements[index].style.width = `${messageElements[index].clientWidth}px`;
  }
}

// Return a new index to swap message in. Should not be the same as the last message type swapped
function getNewSwapIndex() {
  let newMessageIndex = Math.floor(Math.random() * messages.length);
  while (lastMessageType == newMessageIndex) {
    newMessageIndex = Math.floor(Math.random() * messages.length);
  }
  return newMessageIndex;
}

// Get a new message for the message element.
function getNewMessage(toSwapIndex) {
  const messagesArray   = messages[toSwapIndex];
  const previousMessage = messageElements[toSwapIndex].innerText;
  // Get a new random index and the message at that index
  let newMessageIndex = Math.floor(Math.random() * messagesArray.length);
  let newMessage      = messagesArray[newMessageIndex];
  // let's make sure they aren't the same as the message already there
  while (newMessage == previousMessage) {
    newMessageIndex = Math.floor(Math.random() * messagesArray.length);
    newMessage      = messagesArray[newMessageIndex];
  }
  return newMessage;
}
              
            
!
999px

Console