<!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>