js淘宝购物车功能描述：
1、点击“+”，单个商品数量加1，总数量加1；单个商品价格添加，总价也添加。
2.点击“-”，单个商品数量减1，总数量减1；单个商品价格减少，总价也减少。
当该商品数量为0时，点击依然为0；
3.显示出总价，总数量和其中最贵的那个商品的价格。
瞄一眼效果图：
废话不多说，LU代码
<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>无标题文档</title> <style> *{padding:0;margin:0;} #list,p{list-style:none;width:600px;margin:0 auto;} #list li {width:600px;height:50px;line-height:50px;margin-top:20px;font-size:20px;} #list li input{width:60px;height:40px;line-height:40px;} .highlight{color:red;font-size:30px;font-weight:bold;} </style> <script> window.onload = function () { var oUl = $('list'); var totalNumber = $('totalNum'); var totalPrice = $('totalPrice'); var mostExpensive = $('mostExpensive'); var aLi = oUl.getElementsByTagName('li'); var maxPrice = [0]; for ( var i = 0; i < aLi.length; i++ ) { price(aLi[i]); } function price(oLi) { var aBtn = oLi.getElementsByTagName('input'); var oStrong = oLi.getElementsByTagName('strong')[0]; var oEm = oLi.getElementsByTagName('em')[0]; var oSpan = oLi.getElementsByTagName('span')[0]; aBtn[0].onclick = function () { var num = Number(oStrong.innerHTML); var price = parseFloat(oEm.innerHTML); var numbers = Number(totalNumber.innerHTML); var prices = parseFloat(totalPrice.innerHTML); num--; if (num === 0) { // 如果该商品数量为0，,那么就得把它的价格从价格表中清除 var index = maxPrice.indexOf(price); if (index > -1) maxPrice.splice(index, 1); } else if (num < 0) { num = 0; return; } numbers--; oStrong.innerHTML = num; oSpan.innerHTML = num * price + '元'; totalNumber.innerHTML = numbers; totalPrice.innerHTML = prices - (num + 1) * price; mostExpensive.innerHTML = maxPrice[0]; } aBtn[1].onclick = function () { var num = Number(oStrong.innerHTML); var price = parseFloat(oEm.innerHTML); var numbers = Number(totalNumber.innerHTML); var prices = parseFloat(totalPrice.innerHTML); num++; numbers++; if (maxPrice.indexOf(price) < 0) { maxPrice.push(price) maxPrice.sort(function (a,b) {return b - a}); } oStrong.innerHTML = num; oSpan.innerHTML = num * price + '元'; totalNumber.innerHTML = numbers; totalPrice.innerHTML = prices + num * price; mostExpensive.innerHTML = maxPrice[0]; } } function $(id) {return document.getElementById(id);} } </script> </head> <body> <ul> <li> <input type="button" value="-" /> <strong>0</strong> <input type="button" value="+" /> 单价：<em>12.5元</em> 小计：<span>0元</span> </li> <li> <input type="button" value="-" /> <strong>0</strong> <input type="button" value="+" /> 单价：<em>10.5元</em> 小计：<span>0元</span> </li> <li> <input type="button" value="-" /> <strong>0</strong> <input type="button" value="+" /> 单价：<em>8.5元</em> 小计：<span>0元</span> </li> <li> <input type="button" value="-" /> <strong>0</strong> <input type="button" value="+" /> 单价：<em>8元</em> 小计：<span>0元</span> </li> <li> <input type="button" value="-" /> <strong>0</strong> <input type="button" value="+" /> 单价：<em>14.5元</em> 小计：<span>0元</span> </li> </ul> <p> 商品合计共：<span>0</span>件， 共花费了：<span>0</span>元<br /> 其中最贵的商品单是：<span>0</span>元 </p> </body> </html>