Edit in JSFiddle

$('#go').click(function() {
    var $i = $('#text');
    var i = $i[0];
    $i.removeClass("yes");
    $i.removeClass("no");
    
    if (i.value.match(/^[{]?[0-9a-fA-F]{8}[-]?([0-9a-fA-F]{4}[-]?){3}[0-9a-fA-F]{12}[}]?$/)) {
        $i.addClass("yes");
    }
    else {
        $i.addClass("no");
    }
});

<h1>Validating GUIDs with Regular Expressions</h1>

<textarea id="text" style="width:400px;height:50px;">{0C885DD3-7DD9-484B-9B20-3E6552BCA144}</textarea>
<br />
<input type="button" id="go" value="Validate">

.yes { background-color: #afa; }
.no { background-color: #faa; }