<!DOCTYPE html>
<html>
<head>
<title>覆盖</title>
</head>
<body>
<p>2017</p>
<button onclick="fu()">覆盖</button>
<script>
function fu() {
document.write("2018");
}
</script>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<title>覆盖</title>
</head>
<body>
<p>2017</p>
<button onclick="fu()">覆盖</button>
<script>
function fu() {
document.write("2018");
}
</script>
</body>
</html>