​x
 
<!DOCTYPE html>
<html>
<body>
​
<p>在输入字段中按键盘上的 "O" 键来提示一些文本。</p>
​
<input type="text" size="40" onkeypress="myFunction(event)">
​
<p id="demo"></p>
​
<script>
function myFunction(event) {
  var x = event.charCode || event.keyCode;
  if (x == 111 || x == 79) {  // o is 111, O is 79
    alert("You pressed the 'O' key!");
  }
}
</script>
​
</body>
</html>
​