9.数组length

<script type="text/javascript"> var arr=[1,2,3,4,5,6,7,8,9]; var arr2=[]; arr2[20]='abc'; /* 使用下标赋值,前面不存在的元素填充为undefined */ var alen =arr.length; var alen2=arr2.length; document.write(alen+'<br>');<!--结果输出在页面中document为文档节点--> //var arr=[1,2,3,4,5,6,7,8,9]; document.write(arr2.length); for (var i in arr2){ document.write(arr2[i]+'<br>');<!--结果输出在页面中document为文档节点--> }; document.write('<hr>'); for(var i=0;i<alen2;i++){ document.write('arr2['+i+']='+arr2[i]+'<br>'); }; document.write('<hr>'); document.write('测试数组赋值<br>'); var narr =new Array();//首字母大写 for (var i in narr){ document.write(narr[i]+'<br>');<!--结果输出在页面中document为文档节点--> }; narr[0]="abc"; narr[1]=46; narr[3]='like'; for (var i in narr){ document.write(narr[i]+'<br>');<!--结果输出在页面中document为文档节点--> }; for(var i=0;i<narr.length;i++){ document.write('narr['+i+']='+narr[i]+'<br>'); }; </script>