如何获得数组中的元素

var points= [
{p:img_uhr,x:3509103.178,y:5425187.344},
{p:img_uhr,x:3509123.178,y:5425187.344},
{p:img_krankhaus,x:3509143.178,y:5425187.344},
{p:img_uhr,x:3509163.178,y:5425187.344},
{p:img_uhr,x:3509183.178,y:5425187.344},
];
xp[i] = (points[i].x  - lux) / ws.map.scale;
yp[i] = (luy - points[i].y) / ws.map.scale;为什么在　ie 中　x是０，在 ff中没有错误显示。