<html>
<head>
<script src="https://libs.baidu.com/jquery/1.10.2/jquery.min.js">
</script>
<script>
$(document).ready(function(){
$(".btn1").click(function(){
$("p").fadeOut()
});
$(".btn2").click(function(){
$("p").fadeIn();
});
});
</script>
</head>
<body>
<p>This is a paragraph.</p>
<button class="btn1">Fade out</button>
<button class="btn2">Fade in</button>
</body>
</html>