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<html><body><p>A form with a text field that can contain only three letters (no numbers or special characters):</p><form action="/action_page.php"> Country code: <input type="text" id="myText" name="country_code" pattern="[A-Za-z]{3}" title="Three letter country code"> <input type="submit"></form><p>Click the "Try it" button to display the value of the pattern attribute of the text field.</p><button onclick="myFunction()">Try it</button><p id="demo"></p><script>function myFunction() { var x = document.getElementById("myText").pattern; document.getElementById("demo").innerHTML = x;}</script></body></html>