• Identify the three essential pillars of front-end web programming
• Cause a change to given code so that DOM updating effect is seen
• Cause a change to given code so that server-side behavior is stubbed in
• Cause a change to given code so that event listening has an effect

Remember when we started this exploration of the "Simple Liker" application? You might not have been sure that you would make it to this point, but you have. Right now you should have the information needed to create a basic web application!

Your goal is to implement "Simple Liker," from scratch. As a reminder, the final product should look something like this:

Keep in mind, the goal here is not to implement a "pixel-perfect" copy doing HTML and CSS. The focus is the JavaScript code. Make sure you write good HTML and CSS, but manage your time to put the focus on JavaScript.

You might be tempted to look back at previous code, but don't. Use your knowledge and documentation from the internet (if needed), to build the application.

Here's the specification:

• Add the .hidden class to the error modal in the HTML so it does not appear when the page first loads
• When a user clicks on an empty heart ("Recognizing events")
  • Invoke mimicServerCall to simulate making a server request
    • mimicServerCall randomly fails to simulate faulty network conditions
    • When the server returns a failure status
      • Respond to the error using a .catch(() => {}) block after your .then(() => {}) block.
      • Display the error modal by removing the .hidden class
      • Display the server error message in the modal
      • Use setTimeout to hide the modal after 5 seconds (add the .hidden class)
    • When the server returns a success status
      • Change the heart to a full heart
      • Add the .activated-heart class to make the heart appear red
• When a user clicks on a full heart
  • Change the heart back to an empty heart
  • Remove the .activated-heart class
• Keep all your styling rules entirely in style.css. Do not manipulate any .style properties.

Only manipulate the DOM once the server requests respond. Do not make the heart full until you're inside a successful .then block.

Note: The tests will only check for the first part of the specification (adding the hidden class). You should verify the rest of the behavior yourself, by checking the page in the browser.

That's it! Congratulations. You're now a real-deal front-end developer! You can use HTML, CSS, and JavaScript to create living, breathing applications. Every web application front-end you see or have seen is built using these three pillars, which you're now skilled with! Give yourself a well-deserved pat on the back!