如何对数组中的对象进行分组

Question

我有一个对象数组，我想根据两个键对其对象进行分组

var arr = [ 
  {"name": "apple", "id": "apple_0","c":'20'}, 
  {"name": "dog",   "id": "dog_1","c":'10'}, 
  {"name": "apple", "id": "apple_0","c":'30'},
  {"name": "dog",   "id": "dog_1","c":'10'},
];

我期待结果

var final = [ 
  {"name": "apple", "id": "apple_0","c":'50'}, 
  {"name": "dog",   "id": "dog_1","c":'20'}
];

场景是这样的——我想根据name 和id 对对象进行分组。如果在最终数组中找到name 和id，则对其c 求和。

我试过了：

var final = [];
for(var i = 0; i<arr.length; i++){
    var obj = {};
    obj = arr[i];
    for(var j = 0; j<final.length; j++){
        if((obj[name] !== final[j].name) && (obj[id] !== final[j].id)){
          final.push(obj)
        }else{
            //addition of key `c` in existing object in `final` array 
        }
    }
} 

但是内部 for 循环不起作用，并且由于连续循环执行而导致我的系统挂起。

请让我知道如何修复它或任何其他逻辑以获得最终结果。

Answer 1

您实际上可以使用forEach 并在创建新数组之前将元素添加到对象中

var arr = [{
    "name": "apple",
    "id": "apple_0",
    "c": '20'
  },
  {
    "name": "dog",
    "id": "dog_1",
    "c": '10'
  },
  {
    "name": "apple",
    "id": "apple_0",
    "c": '30'
  },
  {
    "name": "dog",
    "id": "dog_1",
    "c": '10'
  },
];
// a new array which be created with updated value
var grouped = [];
arr.forEach(function(a) {
  // check if the element is present
  // if not then add the element
  if (!this[a.id]) {
    this[a.id] = {
      name: a.name,
      id: a.id,
      c: a.c
    };
    grouped.push(this[a.id]);
  } else {
    // if present then add the value of
    this[a.id].c += +a.c;
    
  }
}, Object.create(null));
console.log(grouped)

注意

Answer 2

var arr = [ 
  {"name": "apple", "id": "apple_0","c":'20'}, 
  {"name": "dog",   "id": "dog_1","c":'10'}, 
  {"name": "apple", "id": "apple_0","c":'30'},
  {"name": "dog",   "id": "dog_1","c":'10'},
];


var final = arr.reduce((acc, cur) => {
  var doPush = true;
  acc.map(v => {
    if (v.name === cur.name) {
      v.c = +v.c + +cur.c
      doPush = false;
    }
  });
  if (doPush) {
    acc.push(cur)
  }
  return acc;
}, []);

console.log (final)

Answer 3

这是一个使用 hash table 和 #reduce() 函数的解决方案 - 请参阅下面的演示：

var arr = [{"name": "apple", "id": "apple_0","c":'20'},{"name": "dog",   "id": "dog_1","c":'10'}, {"name": "apple", "id": "apple_0","c":'30'},{"name": "dog",   "id": "dog_1","c":'10'}];

var result = arr.reduce(function(hash){
  return function(p,c){
    if(hash[c.id])
      hash[c.id].c = +hash[c.id].c + +c.c
    else {
      hash[c.id] = hash[c.id] || c;
      p.push(hash[c.id]);
    }
    return p;
  }
}(Object.create(null)), []);

console.log(result);

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Answer 4

您可以通过 id 构建地图，并将所有 c 与 reduce 累加。 类似的东西：

var arr = [{
    "name": "apple",
    "id": "apple_0",
    "c": '20'
  },
  {
    "name": "dog",
    "id": "dog_1",
    "c": '10'
  },
  {
    "name": "apple",
    "id": "apple_0",
    "c": '30'
  },
  {
    "name": "dog",
    "id": "dog_1",
    "c": '10'
  },
];

var mapResult = arr.reduce((acc, item) => {
  item = {...item}; //clone the item
  item.c = parseInt(item.c, 10);

  if (acc[item.id]) {
    acc[item.id].c += item.c
  } else {
    acc[item.id] = item;
  }

  return acc;
}, {});

const result = Object.keys(mapResult).map((key) => mapResult[key]);

console.log(result)

Answer 5

使用Array.prototype.reduce() 和Object.keys() 函数：

var arr = [ 
  {"name": "apple", "id": "apple_0","c":'20'}, 
  {"name": "dog",   "id": "dog_1","c":'10'}, 
  {"name": "apple", "id": "apple_0","c":'30'},
  {"name": "dog",   "id": "dog_1","c":'10'},
],
    groups = arr.reduce(function(r, o){
        var k = o.name +'|'+ o.id;
        (r[k])? r[k] += +o.c : r[k] = +o.c;
        return r;
    }, {}),
    result = Object.keys(groups).map(function(k){ 
        var keys = k.split('|'); 
        return {name: keys[0], id: keys[1], c: groups[k]}; 
     });
    
console.log(result);

Answer 6

var arr = [ 
  {"name": "apple", "id": "apple_0","c":'20'}, 
  {"name": "dog",   "id": "dog_1","c":'10'}, 
  {"name": "apple", "id": "apple_0","c":'30'},
  {"name": "dog",   "id": "dog_1","c":'10'},
];


  arr.reduce(function(cumm, current) {
     var indexNum = cumm.findIndex(x =>{
          return x.name == current.name;
     });      
  if(indexNum > -1) {
    cumm[indexNum].c =  Number(cumm[indexNum].c) + Number(current.c);
  } else {
    cumm.push(current);
  }
   return cumm;
 }, []);

Answer 7

1. obj[属性] eq undifined

   var obj = {name:'John'};
   console.log(obj[name]);

2. if((obj.name !== final[j].name) || (obj[id] !== final[j].id)){
       // 推
   }别的{
       // 代码
   }