js对数据分组类似group by

小鱼儿 2021-09-18 14:40 259阅读 0赞

不得不说很牛

前端处理后端的返回来的json, 对数据进行处理类似group by，看到大牛的写法，分享给大家自己也做一下记录。

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}
    ];

ngOnInit() {
      const sorted = this.groupBy(this.list, function (item) {
        return [item.name];
      });
      console.log(sorted);
    
    }
    
    groupBy(array, f) {
      debugger;
      const groups = {};
      array.forEach(function (o) {
        const group = JSON.stringify(f(o));
        groups[group] = groups[group] || [];
        groups[group].push(o);
      });
      return Object.keys(groups).map(function (group) {
        return groups[group];
      });
    }

处理结果如下:

[
      [
        {
          "name": "John",
          "Average": 15,
          "High": 10,
          "DtmStamp": 1358226000000
        },
        {
          "name": "John",
          "Average": 18,
          "High": 87,
          "DtmStamp": 1358226000000
        },
        {
          "name": "John",
          "Average": 16,
          "High": 87,
          "DtmStamp": 1358226060000
        },
        {
          "name": "John",
          "Average": 17,
          "High": 45,
          "DtmStamp": 1358226060000
        }
      ],
      [
        {
          "name": "Jane",
          "Average": 16,
          "High": 92,
          "DtmStamp": 1358226000000
        },
        {
          "name": "Jane",
          "Average": 17,
          "High": 45,
          "DtmStamp": 1358226000000
        },
        {
          "name": "Jane",
          "Average": 15,
          "High": 10,
          "DtmStamp": 1358226060000
        },
        {
          "name": "Jane",
          "Average": 18,
          "High": 92,
          "DtmStamp": 1358226060000
        }
      ]
    ]

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