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javascript - What is the underlying principle of JS for shopping cart?
習慣沉默
習慣沉默 2017-05-19 10:36:16
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1. What is the underlying principle of the shopping cart? How can the statistics be completed?
2. Use function parameters to create the first half. How to implement the second half?
3. The code is as follows: 

     <!doctype html>
<html>
 <head>
  <meta charset="UTF-8">
  <title>网页标题</title>
  <style>
    li{margin-top:20px;}
  </style>
  <script>
    window.onload = function (){
        var box = document.getElementById("box");
        var aLi = box.getElementsByTagName("li");
        //var oU = document.getElementsByTagName("u");
        function fn(li){
            var aBtn = li.getElementsByTagName("input");
            var oSpan =li.getElementsByTagName("span")[0];
            var oI = li.getElementsByTagName("i")[0];
            var oB = li.getElementsByTagName("b")[0];

            aBtn[1].onclick = function(){
                oSpan.innerHTML++;
                oB.innerHTML = oSpan.innerHTML*oI.innerHTML;
            }
            aBtn[0].onclick = function(){
                if(oSpan.innerHTML>0){
                    oSpan.innerHTML--;
                }
                oB.innerHTML = oSpan.innerHTML*oI.innerHTML;
                }
            }
        
        for(var i=0;i<aLi.length;i++){
            fn(aLi[i]);
            //
        }
    

    }//js最后执行
  </script>
 </head>
 <body>
    <ul id="box">
        <li>
            <input type="button" value="-">
            <span>0</span>
            <input type="button" value="+">
            单价：<i>10</i>元
            小计：<b>0</b>元
        </li>
        <li>
            <input type="button" value="-">
            <span>0</span>
            <input type="button" value="+">
            单价：<i>7.5</i>元
            小计：<b>0</b>元
        </li> 
        <li>
            <input type="button" value="-">
            <span>0</span>
            <input type="button" value="+">
            单价：<i>15</i>元
            小计：<b>0</b>元
        </li> 
        <li>
            <input type="button" value="-">
            <span>0</span>
            <input type="button" value="+">
            单价：<i>20</i>元
            小计：<b>0</b>元
        </li> 
        <li>
            <input type="button" value="-">
            <span>0</span>
            <input type="button" value="+">
            单价：<i>150</i>元
            小计：<b>0</b>元
        </li>
        
    </ul>
 </body>
</html>

The following part: There are n pieces of products in total, the unit price of the most expensive product is a yuan, and how to write the part that costs b yuan in total?
How to assign values ​​to variables and count the final sum of data?
(code and pictures have been pasted)

習慣沉默
習慣沉默

reply all(3)
淡淡烟草味
淡淡烟草味2017-05-19 10:38:16 3 floor

I’ll post all the code. Take a look

   <!doctype html>
    <html>
     <head>
      <meta charset="UTF-8">
      <title>网页标题</title>
      <style>
        li{margin-top:20px;}
      </style>
      <script>
        window.onload = function (){
            // var box = document.getElementById("box");
            // var aLi = box.getElementsByTagName("li");
            // //var oU = document.getElementsByTagName("u");
            // function fn(li){
            //     var aBtn = li.getElementsByTagName("input");
            //     var oSpan =li.getElementsByTagName("span")[0];
            //     var oI = li.getElementsByTagName("i")[0];
            //     var oB = li.getElementsByTagName("b")[0];
    
            //     aBtn[1].onclick = function(){
            //         oSpan.innerHTML++;
            //         oB.innerHTML = oSpan.innerHTML*oI.innerHTML;
            //     }
            //     aBtn[0].onclick = function(){
            //         if(oSpan.innerHTML>0){
            //             oSpan.innerHTML--;
            //         }
            //         oB.innerHTML = oSpan.innerHTML*oI.innerHTML;
            //     }
            // }
            
            // for(var i=0;i<aLi.length;i++){
            //     fn(aLi[i]);
            //     counttotal()
            //     //
            // }
    
            //总和变量
            var total = 0;
            //单价最贵数组
            var mostexp = [];
            //dom 节点
            var box = document.getElementById("box");
            var aLi = box.getElementsByTagName("li");
            var idom = box.getElementsByTagName('i');
            //单价最高
            for(var i=0;i<idom.length;i++){
                mostexp.push(+idom[i].innerHTML)
            }
            document.getElementById('j-exp').innerHTML = Math.max.apply(null,mostexp)
            //绑定加减事件
            function fn(li){
                var oSpan =li.getElementsByTagName("span")[0];
                var oI = li.getElementsByTagName("i")[0];
                var oB = li.getElementsByTagName("b")[0];
                var aBtn = li.getElementsByTagName("input");
    
                for(var i=0,len=aBtn.length;i<len;i++){
                    if(i===0){
                        aBtn[i].onclick = function(){
                            if(oSpan.innerHTML>0){
                                oSpan.innerHTML--;
                            }
                            oB.innerHTML = oSpan.innerHTML*oI.innerHTML;
                            counttotal()
                        }
                    }else{
                        aBtn[i].onclick = function(){
                            oSpan.innerHTML++;
                            oB.innerHTML = oSpan.innerHTML*oI.innerHTML;
                            counttotal()
                        }
                    }
                }    
            }
    
            for(var i=0;i<aLi.length;i++){
                fn(aLi[i]);
            }

            //计算总和
            function counttotal(){
                total = 0;
                var getb = document.getElementsByTagName('b');    
                for(var i=0,len=getb.length;i<len;i++){
                    total+= +getb[i].innerHTML
                }
                document.getElementById('j-total').innerHTML = total
            }
            
        }//js最后执行
      </script>
     </head>
     <body>
        <ul id="box">
            <li>
                <input type="button" value="-">
                <span>0</span>
                <input type="button" value="+">
                单价：<i>10</i>元
                小计：<b>0</b>元
            </li>
            <li>
                <input type="button" value="-">
                <span>0</span>
                <input type="button" value="+">
                单价：<i>7.5</i>元
                小计：<b>0</b>元
            </li> 
            <li>
                <input type="button" value="-">
                <span>0</span>
                <input type="button" value="+">
                单价：<i>15</i>元
                小计：<b>0</b>元
            </li> 
            <li>
                <input type="button" value="-">
                <span>0</span>
                <input type="button" value="+">
                单价：<i>20</i>元
                小计：<b>0</b>元
            </li> 
            <li>
                <input type="button" value="-">
                <span>0</span>
                <input type="button" value="+">
                单价：<i>150</i>元
                小计：<b>0</b>元
            </li>
            
        </ul>
        <!-- 变化 -->
        <p>单价最高：<span id="j-exp">0</span>元</p>
        <p>总计：<span id="j-total">0</span>元</p>
        <!-- 变化 -->
     </body>
    </html>
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Peter_Zhu
Peter_Zhu2017-05-19 10:38:16 2 floor

It’s perfect to write a shopping cart using object-oriented methods. The following is the es6 code

class Cart{
    constructor(){
        //set，map，array，随你选
        this.list = [];
    }
    //将商品加入购物车，需要判断购物车内是否有该商品，
    //以及商品规格是否相同
    add(goods){}
    //将商品移除购物车,这个key可以是id，名称等等，你自己决定
    remove(key){}
    //计算购物车总价，当然，最贵的当然可以计算出来了，排个序就号了
    computeMoney(){}
    //保存购物车，localstorage,服务器，你自己决定，保存之后还是之前更新界面还是你决定
    save(){}
    //清空购物车
    clear(){}
    //购物车是否为空
    isEmpty(){}
    //更多逻辑.......
}

It is best to add hook functions (onSave, onAdd, onRemove....) to each method to achieve reuse and decoupling

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phpcn_u1582
phpcn_u15822017-05-19 10:38:16 1 floor

The principle is that when the user clicks the plus sign on the product selection page, the data is obtained from the data source and put into a new array

var data=res.data;
var shopCar=[];
add(index){//点击加号的时候
    shopCar[index]=data[index] 
}

Then get a new array object, which is the shopping cart list.
Statistics is to add up the price fields in the array object. As for the method you use to add up, it depends on your preference. I use reduce.

If there is a minus sign, there must also be a corresponding subtraction operation.

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