<script>

function getElements(){

    var x=document.getElementsByName("x");

    alert(x.length);

}

</script>

猫:

<input name="x" type="radio" value="猫">

狗:

<input name="x" type="radio" value="狗">

<input type="button" onclick="getElements()" value="多少名称为 'x'的元素?">

​