​x
 
<!DOCTYPE html>
<html>
<body>
​
<p>单击按钮以显示基于时间的问候语：</p>
​
<button onclick="myFunction()">试一试</button>
​
<p id="demo"></p>
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<script>
function myFunction() {
  var hour = new Date().getHours(); 
  var greeting;
  if (hour < 18) {
    greeting = "日安";
  } else {
    greeting = "晚安";
  }
  document.getElementById("demo").innerHTML = greeting;
}
</script>
​
</body>
</html>
​