js表单计算金额问题
<table width="600" border="1" align="center" style="text-align:center;">
<tr>
<td width="102"><input type="checkbox" id="all"/>全选</td>
<td width="203">商品</td>
<td width="119">单价</td>
<td width="148">数量</td>
</tr>
<tr>
<td><input type="checkbox" id="qianbi"/></td>
<td>铅笔</td>
<td>1.5元/支</td>
<td><input type="text" id="qianbi_t" value="1" /></td>
</tr>
<tr>
<td><input type="checkbox" id="yuanzhu" value="" /></td>
<td>圆珠笔</td>
<td>2.5元/支</td>
<td><input type="text" id="yuanzhu_t" value="1" /></td>
</tr>
<tr>
<td><input type="checkbox" id="gangbi" value="" /></td>
<td>钢笔</td>
<td>3元/支</td>
<td><input type="text" id="gangbi_t" value="1" /></td>
</tr>
<tr>
<td colspan="4">金额合计：<span id="m" style="color:#F00;"></span>元 <button>提交订单</button></td>
</tr>
</table>
<script type="text/javascript">
var all=document.getElementById("all");
var qianbi=document.getElementById("qianbi");
var yuanzhubi=document.getElementById("yuanzhu");
var gangbi=document.getElementById("gangbi");
var qb_m=0,yzb_m=0,gb_m=0;
all.onclick=function(){
if(all.checked){
qianbi.checked=true;
yuanzhubi.checked=true;
gangbi.checked=true;
}
else{
qianbi.checked=false;
yuanzhubi.checked=false;
gangbi.checked=false;
}
sub();
};
qianbi.onclick=function(){sub()};
yuanzhubi.onclick=function(){sub()};
gangbi.onclick=function(){sub()};
document.getElementById("qianbi_t").addEventListener("change",function(e){
sub();
});
document.getElementById("yuanzhu_t").addEventListener("change",function(e){
sub();
});
document.getElementById("gangbi_t").addEventListener("change",function(e){
sub();
});
function sub(){
if(qianbi.checked){
qb_m=document.getElementById("qianbi_t").value*1.5
}
else{
qb_m=0;
all.checked=false;
}
if(yuanzhubi.checked){
yzb_m=document.getElementById("yuanzhu_t").value*2.5
}
else{
yzb_m=0;
all.checked=false;
}
if(gangbi.checked){
gb_m=document.getElementById("gangbi_t").value*3
}
else{
gb_m=0;
all.checked=false;
}
var sum=qb_m+yzb_m+gb_m;
document.getElementById("m").innerHTML=sum;
}
</script>