$(this).text()==="Show introduction" displays no instead of yes
<script src="https://cdn.bootcss.com/jquery/3.2.1/jquery.min.js"></script>
<script>
$(function(){
$("#btn").click(function(ev){
if ($(this).text()==="显示简介") {
alert('yes');
}else {
alert('no');
}
});
})
</script>
</head>
<body>
<button id="btn">
显示简介
</button>
<div id="ppt" style="display: none;">11111</div>
</body>
