先上代码
html"><!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>Title</title></head><body>
<H1>我的WEB页面</H1><table border="2px" bgcolor="#7fffd4"><tr><th colspan="2">获取当前时间，如果在上午，返回good morning；如果在下午， 返回 good afternoon</th></tr><tr><script>function sayHi () {// 获取当前时间var current_time = new Date();console.log(`当前时间：${current_time}`);if (current_time.getHours() < 12) {document.getElementById("sayHi").innerHTML = current_time.toString() + "：good morning";} else {document.getElementById("sayHi").innerHTML = current_time.toString() + "：good afternoon";}}</script><td style="width: 20%;"><button type="button" onclick="sayHi()">获取问候语</button></td><td style="width: auto"><p id="sayHi"></p></td></tr>
</table></body>
</html>
通过指定不为空的单元格所占表格宽度比例，实现空单元格的占位
