madeas,
добавление только одного класса, с возможностью отмены.
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
</style>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script>
$(function() {
var b = $('.btn');
b.click(function() {
var that = this;
b.each(function() {
var cls = $(this).data("cls");
that == this ? $('.bSm').toggleClass(cls) : $('.bSm').removeClass(cls)
});
});
});
</script>
</head>
<body>
<style>
body{
background-color: #EEE8AA;
}
.bSm {
display: block;
background: #fff;
width: 150px;
height: 150px;
border-radius: 8px;
margin: 0 auto;
}
.two {
width: 450px;
height: 675px;
border-radius: 38px;
}
.three {
width: 267px;
height: 553px;
border-radius: 18px;
}
</style>
<div class="bSm"></div>
<button class="btn" data-cls="two">2</button>
<button class="btn" data-cls="three">3</button>
<div class="bSres"></div>
</body>
</html>