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<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>JS Alphabet Pattern 21 - Try It</title>
</head>
<body>
  <h1>Diamond Alphabet &amp; Stars</h1>
  <p>Edit the half height or loops, then click Run.</p>
  <pre id="output" style="font-family: monospace; white-space: pre;"></pre>
  <script>
    const alpha = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    let result = "";

    for (let i = 1; i <= 5; i++) {
      let line = "";
      for (let j = 1; j < i * 2; j++) {
        line += (j % 2 === 0) ? "*" : alpha[i - 1];
      }
      result += line + "\n";
    }

    for (let i = 4; i >= 1; i--) {
      let line = "";
      for (let j = 1; j < i * 2; j++) {
        line += (j % 2 === 0) ? "*" : alpha[i - 1];
      }
      result += line + "\n";
    }

    document.getElementById("output").textContent = result;
  </script>
</body>
</html>

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JavaScript Alphabet Pattern 21 (Try It)