一个郁闷的问题，怎么显示不正常

<input name="radio1" type="radio" value="1" onClick="checks()>
<input name="radio1" type="radio" value="2" onClick="checks()>
<input type="button" onClick="checks()">

<script>
    function checks()
    {
        var radios=document.getElementsByName("radio1");
        for(var i=0;i<radios.length;i++)
        {
            if(radios[i].checked==true)
            {
                alert(radios[i].value);
            }
        }
    }

</script>