라디오 버튼 체크 여부

<script type="text/javascript" src="http://code.jquery.com/jquery-1.7.2.min.js"></script>
<script type="text/javascript">
    function checkAnimal(){
        var animal = $(':input[name=animal]:radio:checked').val();


        if( animal ){
            alert(animal+"을 선택했습니다");
            return true;
        }else{
            alert("동물을 선택하세요");
            return false;
        }
    }
</script>
<form onsubmit="return checkAnimal()">
    <input type="radio" name="animal" value="Dog">Dog
    <input type="radio" name="animal" value="Monky">Monky
    <input type="radio" name="animal" value="Cat">Cat
    <input type="radio" name="animal" value="Horse">Horse
    <input type="submit" value="선택">
</form>