javascript验证空白输入框 不起作用！
我有两个页面需要验证 一个是点菜输入数量（type=text），另一个是付款方式（type=radio）
代码：
点菜页面：
echo "<form name='shopping_cart_form' method='post' action='include/shopping_cart_form.php' onsubmit='return dosubmit()'>";echo "<div id='item_details' style=''> <input class='txt_qty' type='text' name='textbox_qty' id='textbox_qty' /> <input class='add_button' type='submit' name='btn_add' id='btn_add' value='Add to Cart' /> </div>"; echo "</form>";
//无论我把这段js放在什么位置，都不起作用，为什么啊？<script language="javascript" type="text/javascript">function dosubmit(){ if(document.shopping_cart_form.textbox_qty.value=="" || document.shopping_cart_form.textbox_qty.value==0) { if(document.shopping_cart_form.btn_add.value=="Add to Cart") { document.shopping_cart_form.textbox_qty.style.borderColor="red"; alert("please fill all fields!"); return false; } }}</script>echo "<form name='submit_form' method='post' action='order_confirmation.php' onsumbit='return isEmpty();'>";//....while(..){ echo "<td style='$time_style'><input type='radio' name='$dest_id_time' value='$pickup_time_id'$disable>$pickup_time_formatted</td>";}echo "<tr><td style='font-size:11.5pt'><input type='radio' name='payment_methods' value='credit' >Pay by Whim Win Credit </td></tr>";echo "<tr><td style='font-size:11.5pt'><input type='radio' name='payment_methods' value='card' >Credit / Debit Card / Paypal </td></tr>";echo "</form>";<script language="javascript">//由于里面有个radio的名字是动态的，所以根浴网友提示，直接遍历所有radio，来判断没checked的选项，但是为什么不起作用啊！！！！？？？？愁死我了<!--function isEmpty(){ var input=document.getElementsByTagName("input"); for(i=0;i<input.length;i++) { if(input[i].type=="radio") { if(input[i].checked == false) alert('Please choose your pick up time and payment method.'); } }}//--></script><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>无标题文档</title></head><body><form name='submit_form' method='post' action='order_confirmation.php' onsubmit='return isEmpty();'> <tr> <td style='border-bottom:3px #4F8A2B solid; color:#6B6B6B'><input type='radio' name='2' value='1' > 11:30</td> <input type='hidden' name='final_invoice_id' value='8731'> <input type='hidden' name='order_time' value='2012-05-03 00:00:45'> <input type='hidden' name='pickup_date' value='03/05/2012'> <input type='hidden' name='display_total_price' value='24.40'> </tr> </table> <p></p> <p style='width:90%;color:#6B6B6B; margin:auto; font-family: Verdana, Arial, Helvetica, sans-serif;'><b>Payment Methods (Please select one of them)</b></p> <table border='0' style='width:90%;color:#6B6B6B; margin:auto'> <tr> <td colspan=2 style='font-size:10.5pt'> You have<a style='color:#d34836'> $4.00 </a>credits left.<a style='color:#d34836' href='recharge.php'>Recharge Now!</a></td> </tr> <tr> <td style='font-size:11.5pt'><input type='radio' name='payment_methods' value='credit' disabled='disabled'> Pay by Whim Win Credit - <a style='color:#d34836' href='recharge.php'>Recharge</a> will receive <a style='color:red'>5% discount off.</a></td> </tr> <tr> <td style='font-size:11.5pt'><input type='radio' name='payment_methods' value='cr_and_card'> $4.00 Whim Win Cr+$20.4 by Credit / Debit Card / Paypal <a href='#' onclick='javascript:window.open('https://www.paypal.com/au/cgi-bin/webscr?cmd=xpt/Marketing/popup/OLCWhatIsPayPal-outside','olcwhatispaypal','toolbar=no, location=no, directories=no, status=no, menubar=no, scrollbars=yes, resizable=yes, width=400, height=350');'><img src='https://www.paypalobjects.com/en_AU/i/bnr/horizontal_solution_PP.gif' border='0' alt='Solution Graphics'></a></td> </tr> <tr> <td style='font-size:11.5pt'><input type='radio' name='payment_methods' value='card'> Credit / Debit Card / Paypal <a href='#' onclick='javascript:window.open('https://www.paypal.com/au/cgi-bin/webscr?cmd=xpt/Marketing/popup/OLCWhatIsPayPal-outside','olcwhatispaypal','toolbar=no, location=no, directories=no, status=no, menubar=no, scrollbars=yes, resizable=yes, width=400, height=350');'><img src='https://www.paypalobjects.com/en_AU/i/bnr/horizontal_solution_PP.gif' border='0' alt='Solution Graphics'></a></td> </tr> </table> <p></p> <p style='width:90%;color:#6B6B6B; margin:auto; text-align:center'> <input id='btn_continue' style='' name='continue_order' type='submit' value='Continue Shopping'> <input id='btn_confirm' style='' name='go_next' type='submit' value='Confirm'> <input name='hidden_credit' type='hidden' value='4.00'> </p> <p></p></form></div><div class="step_num"><b style="color:#d34836">FOLLOWING STEPS</b></div></br><div class="step_num"><b style="color:#d34836">STEP 4</b>: Pay, and remember your invoice ID, we are waiting for you at your pick up time!</div></br><div id="footer"> <p> Offcial Email:<a href="mailto:whimwin@gmail.com">whimwin@gmail.com</a> <br /> Please feel free to email us for any feedback or suggestions, Thank you!</a> <br /> <h4>copyright © Whimwin Pty Ltd.</h4> <br /></div><script type="text/javascript">function isEmpty() { var obj = document.getElementsByTagName('form')[0].getElementsByTagName('input'); var FLAG = { pm: false, //name = "payment_methods" otherRadio: false } for (var i = 0; i < obj.length; i ++) { if (obj[i].type == 'radio') { if (obj[i].name == 'payment_methods') { if (obj[i].checked == true) FLAG.pm = true; } else { if (obj[i].checked == true) FLAG.otherRadio = true; } } } if (!FLAG.pm || !FLAG.otherRadio) { alert('Please choose your pick up time and payment method.'); return false; } else return true;}</script> </body></html>