当时间小于 20:00 时，生成问候 "Good day"

<p>如果时间早于 20:00，会获得问候 "Good day"。</p>

<button onclick="myFunction()">点击这里</button>

<p id="demo"></p>

<script>

  function myFunction() {

    var x = "";

    var time = new Date().getHours();

    if (time < 20) {

      x = "Good day";

    }

    document.getElementById("demo").innerHTML = x;

  }

</script>