​x
 
<!DOCTYPE html>
<html>
<body>
​
<p>在输入字段中按键盘上的某个键，以确定是否按下了 CTRL 键。</p>
​
<input type="text" onkeydown="isKeyPressed(event)">
​
<p id="demo"></p>
​
<script>
function isKeyPressed(event) {
  var x = document.getElementById("demo");
  if (event.ctrlKey) {
    x.innerHTML = "The CTRL key was pressed!";
  } else {
    x.innerHTML = "The CTRL key was NOT pressed!";
  }
}
</script>
​
</body>
</html>
​