下面这个清楚些
<div id=a>qqqq</div>
<script>
var a=document.getElementById("a")
a.innerHTML("aaaaaa");
</script>
<div id=a>qqqq</div>
<script>
var a=document.getElementById("a")
a.innerHTML("aaaaaa");
</script>
调试欢乐多
a.innerHTML = "aaaaaa";