js实现购物车加减和价格运算

<div class="content">    <div class="logo">        <img src="images/dd_logo.jpg"><span onclick="guan()">关闭</span>    </div>    <div class="cartList" id="zong">        <ul>            <li >¥21.90</li>            <li><input type="button" name="minus" value="-" onclick="jian()"><input type="text" name="amount" value="1" id="shang"><input type="button" name="plus" value="+" onclick="jia()"></li>            <li>¥<input type="text" name="price" value="21.90" id="yiqian"></li>            <li><p onclick="shou()">移入收藏</p><p onclick="shan()">删除</p></li>        </ul>        <ul>            <li >¥24.00</li>            <li><input type="button" name="minus" value="-" onclick="jian1()"><input type="text" name="amount" value="1" id="shang1"><input type="button" name="plus" value="+" onclick="jia1()"></li>            <li>¥<input type="text" name="price" value="24.00"id="erqian" ></li>            <li><p onclick="shan()">移入收藏</p><p onclick="shan()">删除</p></li>        </ul>        <ol>            <li id="totalPrice" > 0.00</li>            <li><span onclick="jie()">结 算</span></li>        </ol>    </div>    <h3 id="shijian">现在是：</h3></div>

var price = 0.00;var price1 = 0.00;var price2 = 0.00;function jian() {    var i = parseInt(document.getElementById("shang").valueOf().value) - 1;    if (i <= 0) {        i = 0;    }    document.getElementById("shang").valueOf().value = i;    price1 = 21.90 * i;    document.getElementById("yiqian").value=suan(price1);    zong();}function jia() {    var i = parseInt(document.getElementById("shang").valueOf().value) + 1;    document.getElementById("shang").valueOf().value = i;    price1 = 21.90 * i;    document.getElementById("yiqian").value=suan(price1);    zong();}function jian1() {    var i = parseInt(document.getElementById("shang1").valueOf().value) - 1;    if (i <= 0) {        i = 0;    }    document.getElementById("shang1").valueOf().value = i;    price2 = 24.00 * i;    document.getElementById("erqian").value=suan(price2);    zong();}function jia1() {    var i = parseInt(document.getElementById("shang1").valueOf().value) + 1;    document.getElementById("shang1").valueOf().value = i;    price2 = 24.00 * i;    document.getElementById("erqian").value=suan(price2);    zong();}function suan(number) {    price = price1 + price2;    if (isNaN(number)) {        return false;    }    number = Math.round(number * 100) / 100;    var s = number.toString();    var rs = s.indexOf(".");    if (rs < 0) {        rs = s.length;        s += ".";    }    while (s.length <= rs + 2) {        s += "0";    }    return s;}function zong() {    price = price1 + price2;    if (isNaN(price)) {        return false;    }    price = Math.round(price * 100) / 100;    var s = price.toString();    var rs = s.indexOf(".");    if (rs < 0) {        rs = s.length;        s += ".";    }    while (s.length <= rs + 2) {        s += "0";    }    document.getElementById("totalPrice").innerHTML=s;}