<!DOCTYPE html>
<html>
<head>
<title>Test</title>
<meta charset="utf-8">
</head>
<body>
<div id="div"></div>
<p id="p">
我是文字
<span>123</span>
</p>
</body>
<script type="text/javascript">
var p = document.getElementById("p");
console.log(p.innerText);
console.log(p.innerHTML);
var div = document.getElementById("div");
div.innerHTML = '<strong>今天是：</strong>2021';
div.innerText = '<strong>今天是：</strong>2021';
</script>
</html>
let div_h1 = document.querySelector('.box_shang>h1')
console.log(div_h1.innerHTML, div_h1.innerText)
let div = document.querySelector('div')
div.innerHTML = '<strong>今天是：</strong>2021'