​x
 
<!DOCTYPE html>
<html>
<body>
​
<p>单击这个按钮可显示基于时间的问候语。</p>
​
<button onclick="myFunction()">试一试</button>
​
<p id="demo"></p>
​
<script>
function myFunction() {
  var time = new Date().getHours();
  var greeting;
  if (time < 20) {
    greeting = "Good day";
  } else {
    greeting = "Good evening";
  }
  document.getElementById("demo").innerHTML = greeting;
}
</script>
​
</body>
</html>
​