奇怪的错误: 'bill_company' 未定义 在线等高手解答

Question

function completeBilling(obj) {
  if (obj.shipandbill.checked) {
    bill_company  = obj.bill_company.value;
    bill_first    = obj.bill_first.value;
    bill_last     = obj.bill_last.value;
    bill_country  = obj.bill_country.value;
    bill_street   = obj.bill_street.value;
    bill_suburb   = obj.bill_suburb.value;
    bill_city     = obj.bill_city.value;
    bill_county   = obj.bill_county.value;
    bill_county1  = obj.bill_county1.value;
    bill_zip      = obj.bill_zip.value;
    //bill_phone  = obj.bill_phone.value;
    //bill_fax    = obj.bill_fax.value;
    //bill_email  = obj.bill_email.value;    obj.bill_company.value = obj.ship_company.value;
    obj.bill_first.value   = obj.ship_first.value;
    obj.bill_last.value    = obj.ship_last.value;
    obj.bill_country.value = obj.ship_country.value;
    obj.bill_street.value  = obj.ship_street.value;
    obj.bill_suburb.value  = obj.ship_suburb.value;
    obj.bill_city.value    = obj.ship_city.value;
    obj.bill_county.value  = obj.ship_county.value;
    obj.bill_county1.value = obj.ship_county1.value;
    obj.bill_zip.value     = obj.ship_zip.value;
    //obj.bill_phone.value = obj.ship_phone.value;
    //obj.bill_fax.value   = obj.ship_fax.value;
    //obj.bill_email.value = obj.ship_email.value;
  } else {
    obj.bill_company.value = bill_company;
    obj.bill_first.value   = bill_first;
    obj.bill_last.value    = bill_last;
    obj.bill_country.value = bill_country;
    obj.bill_street.value  = bill_street;
    obj.bill_suburb.value  = bill_suburb;
    obj.bill_city.value    = bill_city;
    obj.bill_county.value  = bill_county;
    obj.bill_county1.value = bill_county1;
    obj.bill_zip.value     = bill_zip;
    //obj.bill_phone.value = bill_phone;
    //obj.bill_fax.value   = bill_fax;
    //obj.bill_email.value = bill_email;
  }
  return true;
}如果把bill_first = obj.bill_first.value;放函数最前面就提示 'bill_first'未定义，但是又不影响整个函数的功能和应用，奇怪了，在线等高手解答

Answer 1

<input name="ship_company" type="text" onChange="completeBilling(this.form)" class="inputA" />
<input name="bill_company" type="text" class="inputA" />这是个很简单的函数呀，所有代码都在这了，就是但用户勾选ship信息和bill信息一致时自动把ship信息赋给bill,让用户不用重新填写，麻烦你们仔细看下
<input type="checkbox" name="shipandbill" value="on" onClick="javascript:completeBilling(this.form)" />