<div?class="food"?id="herd">
???
</div>
<h1?onclick="hattr()">trjtr</h1>
<script>
??function?hattr(){
??????var?anode=document.getElementsByClassName("food");
???????anode[0].setAttribute("id","987");
??????anode[0].setAttribute("class","789");
??}

為什么?? anode[0]??? 就沒有問題；而?? anode?? 就不正確了