求帮修改代码。不知道怎么设置购物车的加减方法，可以使加减不冲突
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function selectall3()
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var a = document.getElementsByTagName("input");
for (var i=0; i<a.length; i++)
if (a[i].type == "checkbox") a[i].checked =!a[i].checked;
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<script>
$(function(){
var t = $("#text_box");
$("#add").click(function(){
t.val(parseInt(t.val())+1)
setTotal();
})
$("#min").click(function(){
t.val(parseInt(t.val())-1)
setTotal();
})
function setTotal(){
$("#total").html((parseInt(t.val())*3.95).toFixed(2));
}
setTotal();
})
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<div id="header_wd">
<div class="c-inav">
<section><div class="btn_back_l"><a href="http://m.jianke.com"><span></span></a></div></section>
<section><span>订单确认</span></section>
<section id="navlist" class="navlist"><img src="images/nav_03.jpg" width="28" height="28"></section>
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$(document).ready(function () {
$("#navlist").toggle(function () { $("#navbox").addClass("navboxshow"); }, function () { $("#navbox").removeClass("navboxshow"); },2000);
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<div id="personal">
<div class="xg2">
<div class="shoppingc_head underline2">
<span class="fl span_con span_left marl20 ">共 <span class="red">2</span> 件商品</span>
<a href="#" onclick="javascript:selectall3()" name=All><div class="bor_radius alls fl border_2 shadebg">全选</div></a>
</div>
<div class="mart15">
<div class="shoppinglist bor_radius border_2 t_a_l">
<div class="list_l fl rel">
<div id="holder" class="cart_dw">
<input type="checkbox" id="checkbox-2-2" class="regular-checkbox big-checkbox" /><label for="checkbox-2-2"></label></div>
<a href="#"><img src="images/waitpain_03.gif" width="14" height="16" class="imgdel_dw"></a>
</div>
<div class="list_c fl bor_radius border_2 rel"><img src="images/waitpain_07.jpg" width="35" height="52" class="imglist_dw"></div>
<div class="list_r fl fn12 rel">
<p>渔夫堡牌胶原蛋白维C粉<br />
规格：2.5g*20袋<br />
<span class="del_line">市场价：￥1700</span><br />
<span class="red">健客价：￥1700</span><br /></p>
数量：
<div class="jj_btn">
<a href="javascript:void(0);" id="min"><div class="fl cir_btn border_2">-</div></a>
<input id="text_box" name="" type="text" value="1" class="fl jj_text"/>
<a href="#" id="add"><div class="fl cir_btn border_2">+</div></a>
</div></div>
<div class="clearfix"></div>
</div>
</div>
<div class="shoppinglist bor_radius border_2 t_a_l">
<div class="list_l fl rel">
<div id="holder" class="cart_dw"><input type="checkbox" id="checkbox-2-1" class="regular-checkbox big-checkbox" /><label for="checkbox-2-1"></label></div>
<a href="#"><img src="images/waitpain_03.gif" width="14" height="16" class="imgdel_dw"></a>
</div>
<div class="list_c fl bor_radius border_2 rel"><img src="images/waitpain_07.jpg" width="35" height="52" class="imglist_dw"></div>
<div class="list_r fl fn12 rel">
<p>渔夫堡牌胶原蛋白维C粉<br />
规格：2.5g*20袋<br />
<span class="del_line">市场价：￥1700</span><br />
<span class="red">健客价：￥1700</span><br /></p>
数量：
<div class="jj_btn" >
<a href="#" id="min" ><div class="fl cir_btn border_2">-</div></a>
<input id="text_box" name="" type="text" value="1" class="fl jj_text"/>
<a href="#" id="add" ><div class="fl cir_btn border_2">+</div></a>
</div></div>
<div class="clearfix"></div>
</div>
<div class="price_detial t_a_l">
<p>已选择<span class="red">3</span>件商品<br />
价 格：¥15.00<br />
优 惠：¥0.00<br />
合 计：¥<span class="red">280.00</span></p>
</div>
<div class="btn9">
<a href="#" >
<span class="con_btn bg_color fl bor_radius4 fn16 white">结 算</span>
</a>
</div>
<div class="btn9">
<a href="#" >
<span class="con_btn fl bor_radius4 fn16 border_2">继续购物</span>
</a>
</div>
</div>
</div>
<footer></footer>
</body>
</html>
<a href="javascript:void(0);" class="min"><div class="fl cir_btn border_2">-</div></a>
<input class="text_box" name="" type="text" value="1" class="fl jj_text"/>
<a href="#" class="add"><div class="fl cir_btn border_2">+</div></a>
$(".add").click(function(){
var t = $(this).parent().find(".text_box");
t.val(parseInt(t.val())+1)
setTotal();
})
$(".min").click(function(){
var t = $(this).parent().find(".text_box")
t.val(parseInt(t.val())-1)
setTotal();
})
