<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<title></title>
<meta charset="utf-8" />
<style>
.cls{
background-color:orange;
border:1px solid red;
}
</style>
<script src="jquery-3.3.1.js"></script>
<script>
$(function () {
$('#btn').click(function () {
//$('p').text('我改变了');//不用遍历，隐私迭代
$('.cls').text('我改变了');
});
});
</script>
</head>
<body>
<input type="button" name="name" value="改变" id="btn" />
<p>床前明月光</p>
<p class="cls">疑是地上霜</p>
<p>举头望明月</p>
<p>低头思故乡</p>
</body>
</html>
