01.<script language="javascript">
02. function test(Quality,Stock){
03.
04. var Qty=document.getElementById(Quanlity).value;
05. var Stock=document.getElementById(Stock).value;
06.
07. if(Stock-Qty<0){
08. alert('สินค้าไม่เพียงพอ');
09. return false;
10. }
11. }
12.
13.
14.</script>
15.
16.
17.<form id="f1" method="post" action="?" onsubmit="return test('Quanltiy','Stock')">
18. <input type="text" name="Quanlity" id="Quanlity" value="" />
19. <input type="hidden" name="Stock" id="Stock" value="10" />
20. <input type="submit"/>
21.</form>
