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<!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>