​x
 
<!DOCTYPE html>
<html>
<body>
​
<p>具有只能包含三个字母（无数字或特殊字符）的文本字段的表单：</p>
​
<form action="/demo/htmldom/action_page.php">
  Country code: <input type="text" id="myText" name="country_code" pattern="[A-Za-z]{3}" title="三字母国家代码">
  <input type="submit">
</form>
​
<p>点击“试一试”按钮，显示文本域的pattern属性值。</p>
​
<button onclick="myFunction()">试一试</button>
​
<p id="demo"></p>
​
<script>
function myFunction() {
  var x = document.getElementById("myText").pattern;
  document.getElementById("demo").innerHTML = x;
}
</script>
​
</body>
</html>
​