请问var x=document.getElementsByTagName("div")[0].childNodes;里的[0]是什么意思？
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>无标题文档</title>
</head>
<body>
<div>
javascript
<p>javascript</p>
<div>jQuery</div>
<h5>PHP</h5>
</div>
<script type="text/javascript">
var x=document.getElementsByTagName("div")[0].childNodes;
for(var i=0;i<x.length;i++){
document.write(x[i]+' ');
document.write(x[i].nodeType+'<br />')
}
</script>
</body>
</html>
