<p>点击按钮根据时间输出问候语</p>

<button onclick="myFunction()">点我</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>

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