7.for循环及for(in)
<![CDATA[
<script type="text/javascript">
var arr=[1,2,3,4,5,6,7,8,9];
for (var i=0;i<9;i++){
document.write(arr[i]+'<br>');<!--结果输出在页面中document为文档节点-->
}
document.write('<hr>');
//var arr=[1,2,3,4,5,6,7,8,9];
for (var j in arr){//j为arr下标
document.write(arr[j]+'<br>');<!--结果输出在页面中document为文档节点-->
}
</script>
]]>