jQuery doc
.attr()
Get the value of an attribute for the first element in the set of matched elements or set one or more attributes for every matched element.
<!DOCTYPE html>
<html lang="ja">
<head>
<meta charset="utf-8">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>二次元バーコード</title>
<style>
body {
}
</style>
</head>
<body>
<h1>二次元バーコード</h1>
<p>
<input type="text" id="msg">
<input type="button" value="変換" id="button">
</p>
<div id="barCode"></div>
<script>
$(function(){
$('#button').click(function(){
var msg = encodeURIComponent($('#msg').val());
var img = $('<img>').attr('src', 'http://chart.apis.google.com/chart?cht=qr&chs=150x150&choe=Shift_JIS&chl='+msg);
$('#barCode').html(img);
});
});
</script>
</body>
</html>
