JavaScript实现类似淘宝的购物车效果

<table id="cartTable">
 <thead>
 <tr>
 <th><label><input class="check-all check" type="checkbox"/>&nbsp;全选</label></th>
 <th>商品</th>
 <th>单价</th>
 <th>数量</th>
 <th>小计</th>
 <th>操作</th>
 </tr>
 </thead>
 <tbody>
 <tr>
 <td class="checkbox"><input class="check-one check" type="checkbox" /></td>
 <td class="goods"><img src="/UploadFiles/2021-04-02/1.jpg">

css代码：


*{
 margin: 0;
 padding: 0;
 }
 a{
 color: #666;
 text-decoration: none;
 }
 body{
 padding:20px;
 color: #666;
 }
 .fl{
 float: left;
 }
 .fr{
 float: right;
 }
 table{
 border-collapse: collapse;
 border-spacing: 0;
 border: 0;
 text-align: center;
 width: 937px;
 }
 th,td{
 border: 1px solid #cadeff;
 }
 th{
 background: #e2f2ff;
 border-top: 3px solid #a7cbff;
 height: 30px;
 }
 td{
 padding: 10px;
 color: #444;
 }
 tbody tr:hover{
 background: RGB(238,246,255);
 }
 .checkbox{width: 60px;}
 .goods{width: 300px;}
 .goods span{
 width: 180px;
 margin-top: 20px;
 text-align: left;
 float: left;
 }
 .price{width: 130px;}
 .count{width: 90px;}
 .count .add, .count input, .count .reduce{
 float: left;
 margin-left: -1px;
 position: relative;
 z-index: 0;
 }
 .count .add, .count .reduce{
 height: 23px;
 width: 17px;
 border: 1px solid #e5e5e5;
 background: #f0f0f0;
 text-align: center;
 line-height: 23px;
 color: #444;
 }
 .count .add:hover, .count .reduce:hover{
 color: #f50;
 z-index: 3;
 border-color: #f60;
 cursor: pointer;
 }
 .count input{
 width: 50px;
 height: 15px;
 line-height: 15px;
 border: 1px solid #aaa;
 color: #343434;
 text-align: center;
 padding: 4px 0;
 background-color: #fff;
 z-index: 2;
 }
 .subtotal{
 width: 150px;
 color: red;
 font-weight: bold;
 }
 .operation{width: 80px;}
 .operation span:hover, .a:hover{
 cursor: pointer;
 color: red;
 text-decoration: underline;
 }
 img{
 width: 100px;
 height: 80px;
 margin-right: 10px;
 float: left;
 }
 .foot{
 width: 935px;
 margin-top: 10px;
 color: #666;
 height: 48px;
 border: 1px solid #c8c8c8;
 background-image: linear-gradient(RGB(241,241,241),RGB(226,226,226));
 position: relative;
 z-index: 8;
 }
 .foot div, .foot a{
 line-height: 48px;
 height: 48px;
 }
 .foot .select-all{
 width: 100px;
 height: 48px;
 line-height: 48px;
 padding-left: 5px;
 color: #666;
 }
 .foot .closing{
 border-left: 1px solid #c8c8c8;
 width: 100px;
 text-align: center;
 color: #000;
 font-weight: bold;
 background: RGB(238,238,238);
 cursor: pointer;
 }
 .foot .total{
 margin: 0 20px;
 cursor: pointer;
 }
 .foot #priceTotal, .foot #selectedTotal{
 color: red;
 font-family: "微软雅黑";
 font-weight: bold;
 }
 .foot .select{
 cursor: pointer;
 }
 .foot .select .arrow{
 position: relative;
 top: -3px;
 margin-left: 3px;
 }
 .foot .select .down{
 position: relative;
 top: 3px;
 display: none;
 }
 .show .select .down{
 display: inline;
 }
 .show .select .up{
 display: none;
 }
 .foot .select:hover .arrow{
 color: red;
 }
 .foot .selected-view{
 width: 935px;
 border: 1px solid #c8c8c8;
 position: absolute;
 height: auto;
 background: #fff;
 z-index: 9;
 bottom: 48px;
 left: -1px;
 display: none;
 }
 .show .selected-view{display: block;}
 .foot .selected-view div{height: auto;}
 .foot .selected-view .arrow{
 font-size: 16px;
 line-height: 100%;
 color: #c8c8c8;
 position: absolute;
 right: 330px;
 bottom: -9px;
 }
 .foot .selected-view .arrow span{
 color: #fff;
 position: absolute;
 left: 0;
 bottom: 1px;
 }
 #selectedViewList{
 padding: 20px;
 margin-bottom: -20px;
 }
 #selectedViewList div{
 display: inline-block;
 position: relative;
 width: 100px;
 height: 80px;
 border: 1px solid #ccc;
 margin: 10px;
 }
 #selectedViewList div span{
 display: none;
 color: #fff;
 font-size: 12px;
 position: absolute;
 top: 0;
 right: 0;
 width: 60px;
 height: 18px;
 line-height: 18px;
 text-align: center;
 background: RGBA(0,0,0,.5);
 cursor: pointer;
 }
 #selectedViewList div:hover span{
 display: block;
 }


js部分：
1）实现商品的全选功能及数量和价格的计算


var cartTable = document.getElementById('cartTable');
 var tr = cartTable.children[1].rows;//获取table下的tbody下的每一行
 var checkInputs = document.getElementsByClassName('check');
 var checkAllInputs = document.getElementsByClassName('check-all');
 var selectedTotal = document.getElementById('selectedTotal');
 var priceTotal = document.getElementById('priceTotal');
 //计算总数和价格
 function getTotal(){
 var selected = 0;
 var price = 0;
 for(var i=0;i < tr.length; i++){
 if(tr[i].getElementsByTagName('input')[0].checked){
  selected += parseInt(tr[i].getElementsByTagName('input')[1].value);
  price += parseFloat(tr[i].cells[4].innerHTML);//cells属性为获得tr下面的td
 }
 }
 selectedTotal.innerHTML = selected;
 priceTotal.innerHTML = price.toFixed(2);//保留两位小数
 }
 for(var i=0;i<checkInputs.length;i++){
 checkInputs[i].onclick = function(){
 if(this.className === 'check-all check'){//如果点击的是全选按钮，则使所有按钮的状态和它相同
  for(var j=0;j<checkInputs.length;j++){
  checkInputs[j].checked = this.checked;
  }
 }
 if(this.checked == false){//如果其中一个变为未选中状态，则使全选按钮取消选中
  for(var i=0;i<checkAllInputs.length;i++){
  checkAllInputs[i].checked = false;
  }
 }
 getTotal();
 }
 }


2)点击已选商品实现商品预览浮层的功能
点击已选商品时会显示出已选择商品的列表
同时在getTotal()函数中增加新创建的div
js代码：


function getTotal(){
 var selected = 0;
 var price = 0;
 var HTMLstr = '';
 for(var i=0;i < tr.length; i++){
 if(tr[i].getElementsByTagName('input')[0].checked){
  tr[i].className = 'on';
  selected += parseInt(tr[i].getElementsByTagName('input')[1].value);
  price += parseFloat(tr[i].cells[4].innerHTML);//cells属性为获得tr下面的td
  HTMLstr += '<div><img src="/UploadFiles/2021-04-02/'+ tr[i].getElementsByTagName('img')[0].src + '">

 3)商品列表中的取消选择与事件代理
已选商品列表中没有appendChild的时候div和span都不存在，所以要使用事件代理。


selectedViewList.onclick = function(e){
  var el = e.srcElement;
  if(el.className == 'del'){
  var index = el.getAttribute('index');
  var input = tr[index].getElementsByTagName('input')[0];
  input.checked = false;
  input.onclick();
  }
 }


4）实现增减商品数量及小计价格的计算


//增减商品数量事件代理
 for(var i=0;i<tr.length;i++){
  tr[i].onclick = function(e){
  e = e|| window.event;
  var el = e.srcElement;
  var cls = el.className;
  var input = this.getElementsByTagName('input')[1];
  var val = parseInt(input.value);
  var reduce = this.getElementsByTagName('span')[1];
  switch (cls){
   case 'add':
   input.value = val + 1;
   reduce.innerHTML = '-';
    getsubTotal(this);
   break;
   case 'reduce':
   if(val > 1){
    input.value = val - 1;
    getsubTotal(this);
   }else{
    reduce.innerHTML = '';
   }
  }
  getTotal();
  }
  tr[i].getElementsByTagName('input')[1].onkeyup = function(){
  var val = parseInt(this.value);
  var tr = this.parentNode.parentNode;//this指的是当前的input，其父节点的父节点就是当前的tr
  var reduce = tr.getElementsByTagName('span')[1];
  if(isNaN(val) || val < 1){
   val = 1;
  }
  this.value = val;//保证输入框中都是大于1的纯数字
  if(val <= 1){
   reduce.innerHTML = '';
  }
  else{
   reduce.innerHTML = '-';
  }
  getsubTotal(tr);
  getTotal();
  }
 }


 5）实现删除商品功能
学会用for循环删除数组中的一些数据时要回置下标 i 。


//删除商品
 deleteAll.onclick = function(){
  if(selectedTotal.innerHTML != '0'){
  var conf = confirm("确定要删除所选商品吗");
  if(conf){
   for(var i=0;i<tr.length;i++){
   var input = tr[i].getElementsByTagName('input')[0];
   if(input.checked){
    tr[i].parentNode.removeChild(tr[i]);
    i --;//因为删除数组中的一个后，后面的索引就会向前移，此时要让i也向前移一个，回置下标i
   }
   }
   getTotal();
  }
  }
 }


总结
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