<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width">
<title>Balonik</title>
<style>
.balonik {
background-color: #000;
color: #fff;
display: flex;
justify-content: center;
align-items: center;
height: 40px;
}
</style>
</head>
<body>
<div id="balonik_test" style="width: 200px" class="balonik">pomęcz mnie</div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<script>
$('#balonik_test').on({
'mouseover' : function() {
$(this).animate({width:300}, 500);
},
'mouseout' : function() {
$(this).animate({width:200}, 500);
}
});
</script>
</body>
</html>
W jednym pliku aby uprościć wstawianie kodu.