Open file
<body>
<div id="container">
<div class="undo-redo-buttons">
<button class="undo-button" title="Undo">&#x293A;</button>
<button class="redo-button" title="Redo">&#x293B;</button>
<button class="reload-button" title="Reload this demo">&#x21BB;</button>
</div>
<div class="demo-container">
<!-- This is the object of interest -->
<textarea name="demo-textarea" id="demo-textarea" cols="48" rows="4"></textarea>
</div>
</div>

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<script>window.jQuery || document.write("<script src='../js/jquery.min.js'>\x3C/script>")</script>
<script src="../js/underscore.js"></script>
<script src="../js/backbone.js"></script>
<script src="../js/Backbone.Undo.js"></script>

<script src="../js/demo-textarea.js"></script>
<script>
(function ($, Backbone, _) {
var undoManager = new Backbone.UndoManager({
track: true,
register: window.demoTextarea
});
$(".undo-button").click(function () {
undoManager.undo();
});
$(".redo-button").click(function () {
undoManager.redo();
});

$(".reload-button").click(function () {
window.location.reload();
});
})(window.jQuery, window.Backbone, window._);
</script>
</body>