jquery怎么遍历数组

var arr = new Array(13.5,3,4,5,6);
for(var i=0;i<arr.length;i++){
 arr[i] = arr[i]/2.0;
}

var x
var mycars = new Array()
mycars[0] = "Saab"
mycars[1] = "Volvo"
mycars[2] = "BMW"
for (x in mycars)
{
  document.write(mycars[x] + "<br />")
}

var arr=new Array();
arr=["aaa","bbb","ccc"];
$.each(arr,function(index,value){
     alert(i+"..."+value);
});

$(function () {
    $.each([["aaa", "bbb", "ccc"], ["ddd", "eee", "fff"], ["ggg", "hhh", "iii"]], function (index, item) {
         alert(index + "..." + item);
         //输出0...aaa,bbb,ccc  1...ddd,eee,fff  2...ggg,hhh,iii   这时的index为数组下标,item相当于取这二维数组中的每一个数组
         $.each(item, function (index, itemobj) {
              alert(index + "....." + itemobj);
         });
    });
     //输出0...aaa,bbb,ccc  0...aaa 1...bbb 2...cccc  1...ddd,eee,fff  0...ddd 1...eee 2...fff  2...ggg,hhh,iii 0...ggg 1...hhh 2...iii
 });