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<!DOCTYPE html> <html> <body> <p>A form with a text field that can contain only three letters (no numbers or special characters):</p> <form action="demo_form.asp"> 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>