​x
 
<!DOCTYPE html>
<html>
<body>
​
<p>单击按钮显示 "Good day"，仅当时间小于 20:00 时。</p>
​
<button onclick="myFunction()">试一试</button>
​
<p id="demo"></p>
​
<script>
function myFunction() {
  var time = new Date().getHours();
  if (time < 20) {
    document.getElementById("demo").innerHTML = "Good day";
  }
}
</script>
​
</body>
</html>
​