CodePen Embed - Fix ReferenceError: X is not defined in JavaScript

<div>
  <h3>ReferenceError Demo</h3>
  <p>Open the console (F12) to see the error in action.</p>
  <p>Learn how to fix this error! Visit my blog: <a href="https://www.devsky.net/2025/03/solving-javascript-referenceerror-x-is.html" target="_blank" style="color: #1976d2; text-decoration: none;">Fix ReferenceError Guide</a></p>
</div>

body {
  font-family: Arial, sans-serif;
  padding: 20px;
  background-color: #f5f5f5;
}
h3 {
  color: #d81b60;
}
p {
  color: #424242;
}

// This will trigger "ReferenceError: undefinedVar is not defined"
undefinedVar(); // Attempting to call an undefined variable

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