用ecshop开源程序，js里取不到页面的值

代码如下，了解的哥们加我QQ113900176（注明csdn）
/* *

• 添加商品到购物车
  */
  function addToCart(goodsId, parentId)
  {

  var goods = new Object();
  var spec_arr = new Array();
  var fittings_arr = new Array();
  var number = 1;
  var formBuy = document.forms['ECS_FORMBUY'];
  var quick = 0;

  var fid = "goods_number_"+goodsId;
  if(document.getElementById(fid)){
  number = document.getElementById(fid).value;
  }

  // 检查是否有商品规格
  if (formBuy)
  {
  spec_arr = getSelectedAttributes(formBuy);

  if (formBuy.elements['number'])
  {
  number = formBuy.elements['number'].value;
  }

  quick = 1;
  }

  goods.quick = quick;
  goods.spec = spec_arr;
  goods.goods_id = goodsId;
  goods.number = number;
  goods.parent = (typeof(parentId) == "undefined") ? 0 : parseInt(parentId);

  Ajax.call('flow.php?step=add_to_cart', 'goods=' + goods.toJSONString(), addToCartResponse, 'POST', 'JSON');
  }