7.for循环及for(in)

<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>