<style type="text/css">
.hi {
200px;
height: 18vw;
background-color: pink;
font-weight: bold;
font-size: 24px;
overflow: hidden;
}
button {
border: 1px solid red;
padding: 10px;
margin: 10px 0 0 66px;
}
</style>
</head>
<body>
<div class="hi">
<p>hello world1!</p>
<p>hello world2!</p>
<p>hello world3!</p>
<p>hello world4!</p>
<p>hello world5!</p>
<p>hello world6!</p>
<p>hello world7!</p>
</div>
<button>more</button>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.5.2/jquery.min.js" type="text/javascript"></script>
<script type="text/javascript">
$('button').click(function() {
var obj=$('.hi').height();
if(obj=='180'){
$('.hi').height('auto');
} else {
$('.hi').height('180px');
}
});
</script>