js对数组分组处理

一、js数组分组

1.js对数据分组类似group by

源码如下：

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>jquery 数组按某一字段分组</title>
    <!-- <script src="./Scripts/jquery-3.3.1.min.js"></script> -->
    <script src="./Scripts/jquery-1.10.2.min.js"></script>
</head>
<body>
    <script type="text/javascript">
     $(function()
     {
         let a = null;
         let aa = a?a:0;
         console.log(aa);
         let b = undefined;
         let bb = b?b:0;
         console.log(bb);
         let c = '';
         let cc = c?c:0;
         console.log(cc);

        list = [
        {"name": "John", "Average": 15, "High": 10, "DtmStamp": 1358226000000},
        {"name": "Jane", "Average": 16, "High": 92, "DtmStamp": 1358226000000},
        {"name": "Jane", "Average": 17, "High": 45, "DtmStamp": 1358226000000},
        {"name": "John", "Average": 18, "High": 87, "DtmStamp": 1358226000000},
        {"name": "Jane", "Average": 15, "High": 10, "DtmStamp": 1358226060000},
        {"name": "John", "Average": 16, "High": 87, "DtmStamp": 1358226060000},
        {"name": "John", "Average": 17, "High": 45, "DtmStamp": 1358226060000},
        {"name": "Jane", "Average": 18, "High": 92, "DtmStamp": 1358226060000}
        ];
        const sorted =groupBy(list, function (item) {
            return [item.name];//按照name进行分组
        });
        console.log(sorted);
     })
    function  groupBy(array, f) 
    {
        debugger;
        const groups = {};        
        array.forEach(function (o) { //注意这里必须是forEach 大写
            const group = JSON.stringify(f(o));
            groups[group] = groups[group] || [];
            groups[group].push(o);
        });
        return Object.keys(groups).map(function (group) {
            return groups[group];
        }); 
    }    
    </script>
</body>
</html>

具体实现思路：

1.函数groupBy有两个形参，一为对象数组，二为匿名函数（该函数功能：返回对象的某个指定属性的属性值并存放在数组中）；
2.groupBy函数内，先创建一个空对象；
3.然后forEach遍历对象数组，遍历时要执行的函数中只有一个形参o（数组中的每个元素）；
4.由于下面函数调用是想用name来分组，因此let group = JSON.stringify( f(o) )，相当于先获取到对象数组list中的name属性对应的属性值并放入数组中：["John"]，然后再将属性值转换为json字符串：'["John"]'；
5.groups[group] = groups[group] || []，在js中对象也是关联数组，因此这里相当于做了两件事，一是把group作为groups的key，二是将对应的value初始化，第一次执行为空数组，循环执行时找到相同的name时保持不变；
6.groups[group].push( o )，这句相当于把list中每个对象压入数组中作为value；
7.最后，Object.keys(groups)是取出groups对象中的所有key，然后遍历一个个key组成的新数组，返回分好了组的二维数组

2.js根据json数据中的某一个属性来给数据分组

源码如下：

 <!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8">
        <title></title>
    </head>
    <body>
        <span id ="span" style="width: 50px;height: 200px;"></span>
    </body>
    <script>
    var arr = [{"Group":1,"Groupheader":"质量管理","Leftimg":"","Left":"","Min":"","Right":"","Rightimg":""},
{"Group":1,"Groupheader":"","Leftimg":"","Left":"","Min":"质量巡检","Right":"","Rightimg":""},
{"Group":2,"Groupheader":"设备管理","Leftimg":"","Left":"","Min":"","Right":"","Rightimg":""},
{"Group":2,"Groupheader":"","Leftimg":"","Left":"","Min":"设备专业点检","Right":"","Rightimg":""},
{"Group":2,"Groupheader":"","Leftimg":"","Left":"","Min":"设备日检","Right":"","Rightimg":""},
{"Group":2,"Groupheader":"","Leftimg":"","Left":"","Min":"设备周检","Right":"","Rightimg":""},
{"Group":2,"Groupheader":"","Leftimg":"","Left":"","Min":"设备月检","Right":"","Rightimg":""}];
 
var map = {},
    dest = [];
for(var i = 0; i < arr.length; i++){
    var ai = arr[i];
    if(!map[ai.Groupheader]){
        dest.push({
            Groupheader: ai.Groupheader,      
            data: [ai]
        });
        map[ai.Groupheader] = ai;
    }else{
        for(var j = 0; j < dest.length; j++){
            var dj = dest[j];
            if(dj.Groupheader == ai.Groupheader){
                dj.data.push(ai);
                break;
            }
        }
    }
}
console.log(JSON.stringify(dest));
    var sapn = document.getElementById("span");
    span.innerHTML = JSON.stringify(dest);
    </script>
</html>

js对数组分组处理

1.js对数据分组类似group by

2.js根据json数据中的某一个属性来给数据分组

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