JavaScript中自定义函数以及文本框、radio、下拉框的值的获取，结合淘宝竞拍案例来理解。。。

 1     <script type="text/javascript">
 2             function Pay(){
 3                 var Price=2000;
 4                 var AddPrice = document.getElementById("AddPrice").value;
 5                 if(AddPrice=="")
 6                 {
 7                     document.getElementById("span2").innerHTML=‘<font color="red">亲，请输入加的价格哦</font>‘; 
 8                 }
 9                 var num = document.getElementById("num").value;
10                 if(num=="")
11                 {
12                     document.getElementById("span3").innerHTML=‘<font color="red">亲，请输入您要拍的数量哦</font>‘;
13                 }
14                 var sex = sex1.checked ? ‘男‘ : ‘女‘;
15                  var totalMoney;
16                 var Pay1 = document.getElementById("Pay1");
17                 var index = Pay1.selectedIndex;
18                 switch(index) {
19                     case 0:
20                         document.getElementById("span1").innerHTML=‘<font color="red">微信支付打九折</font>‘; 
21                         totalMoney = (parseInt(Price) + parseInt(AddPrice)) * parseInt(num)*0.9;
22                         break;
23                     case 1:
24                         document.getElementById("span1").innerHTML=‘<font color="red">支付宝支付打八折</font>‘;
25                         totalMoney = (parseInt(Price) + parseInt(AddPrice)) * parseInt(num)*0.8;
26                         break;
27                     case 2:
28                         document.getElementById("span1").innerHTML=‘<font color="red">银联支付打七折</font>‘;
29                         totalMoney = (parseInt(Price) + parseInt(AddPrice)) * parseInt(num)*0.7;
30                         break;
31                     case 3:
32                         document.getElementById("span1").innerHTML=‘<font color="red">QQ支付打九折</font>‘;
33                         totalMoney = (parseInt(Price) + parseInt(AddPrice)) * parseInt(num)*0.9;
34                         break;
35                     case 4:
36                         document.getElementById("span1").innerHTML=‘<font color="red">刷卡支付不打折</font>‘;
37                         totalMoney = (parseInt(Price) + parseInt(AddPrice)) * parseInt(num);
38                         break;
39                         default:document.getElementById("span1").innerHTML=‘<font color="red" >亲，支付方式可以进行选择的呦</font>‘;
40                 }
41               if(totalMoney==undefined)
42               {
43                   document.getElementById("span5").innerHTML=‘<font color=red>总价无法计算呦</font>‘;
44               }else
45               {
46                   document.getElementById("TotalPrice").value=totalMoney;
47               }
48                 
49             }
50         
51         </script>