$(document).ready(function(){
$('#toggle').click(function(){
$('.left').animate({width:'toggle'},350);
});
});
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>toggle-jquery1.9</title>
</head>
<body>
<div class="container">
<div class="left"></div>
</div>
<button id="toggle">toggle</button>
</body>
</html>
div.container {
height: 320px;
border: 1px solid #ccc;
}
div.left {
width: 200px;
height: 300px;
background-color: #36f;
}