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 />")

}