通过数组中的多个属性对对象进行分组，然后对其值求和

Question

通过多个属性对数组中的元素进行分组最符合我的问题，因为它确实通过数组中的多个键对对象进行了分组。问题是此解决方案无法汇总属性值，然后删除重复项，而是将所有重复项嵌套在二维数组中。

预期行为

我有一个对象数组，必须按shape和进行分组color。

var arr = [
    {shape: 'square', color: 'red', used: 1, instances: 1},
    {shape: 'square', color: 'red', used: 2, instances: 1},
    {shape: 'circle', color: 'blue', used: 0, instances: 0},
    {shape: 'square', color: 'blue', used: 4, instances: 4},
    {shape: 'circle', color: 'red', used: 1, instances: 1},
    {shape: 'circle', color: 'red', used: 1, instances: 0},
    {shape: 'square', color: 'blue', used: 4, instances: 5},
    {shape: 'square', color: 'red', used: 2, instances: 1}
];

这个数组中的对象被视为重复仅当其shape和color是相同的。如果它们是，我想分别总结它们的used和instances值，然后删除重复项。

因此，在这个例子的结果阵列可以仅含有四种组合：square red，square blue，circle red，circle blue

问题

我在这里尝试了一种更简单的方法：

var arr = [

    {shape: 'square', color: 'red', used: 1, instances: 1},

    {shape: 'square', color: 'red', used: 2, instances: 1},

    {shape: 'circle', color: 'blue', used: 0, instances: 0},

    {shape: 'square', color: 'blue', used: 4, instances: 4},

    {shape: 'circle', color: 'red', used: 1, instances: 1},

    {shape: 'circle', color: 'red', used: 1, instances: 0},

    {shape: 'square', color: 'red', used: 4, instances: 4},

    {shape: 'square', color: 'red', used: 2, instances: 2}

];



result = [];



arr.forEach(function (a) {

    if ( !this[a.color] && !this[a.shape] ) {

        this[a.color] = { color: a.color, shape: a.shape, used: 0, instances: 0 };

        result.push(this[a.color]);

    }

    this[a.color].used += a.used;

    this[a.color].instances += a.instances;

}, Object.create(null));



console.log(result);

但它输出

[{shape: "square", color: "red", used: 11, instances: 9},
{shape: "circle", color: "blue", used: 4, instances: 4}]

而不是预期的结果：

[{shape: "square", color: "red", used: 5, instances: 3},
{shape: "circle", color: "red", used: 2, instances: 1},
{shape: "square", color: "blue", used: 11, instances: 9},
{shape: "circle", color: "blue", used: 0, instances: 0}]

如何获得按形状和颜色正确分组对象的功能？即总结他们的价值，并删除重复的？

Answer 1

将Array＃reduce与帮助器对象一起使用可以对相似的对象进行分组。对于每个对象，检查合并的shape和是否color存在于帮助器中。如果不是，请使用Object＃assign添加到帮助器中以创建对象的副本，然后将其压入数组。如果是这样，请将其值添加到used和instances。

var arr = [{"shape":"square","color":"red","used":1,"instances":1},{"shape":"square","color":"red","used":2,"instances":1},{"shape":"circle","color":"blue","used":0,"instances":0},{"shape":"square","color":"blue","used":4,"instances":4},{"shape":"circle","color":"red","used":1,"instances":1},{"shape":"circle","color":"red","used":1,"instances":0},{"shape":"square","color":"blue","used":4,"instances":5},{"shape":"square","color":"red","used":2,"instances":1}];



var helper = {};

var result = arr.reduce(function(r, o) {

  var key = o.shape + '-' + o.color;



  if(!helper[key]) {

    helper[key] = Object.assign({}, o); // create a copy of o

    r.push(helper[key]);

  } else {

    helper[key].used += o.used;

    helper[key].instances += o.instances;

  }



  return r;

}, []);



console.log(result);

如果你可以使用ES6，您可以使用地图收集的值，然后将其转换回一个数组蔓延的地图＃值：

const arr = [{"shape":"square","color":"red","used":1,"instances":1},{"shape":"square","color":"red","used":2,"instances":1},{"shape":"circle","color":"blue","used":0,"instances":0},{"shape":"square","color":"blue","used":4,"instances":4},{"shape":"circle","color":"red","used":1,"instances":1},{"shape":"circle","color":"red","used":1,"instances":0},{"shape":"square","color":"blue","used":4,"instances":5},{"shape":"square","color":"red","used":2,"instances":1}];



const result = [...arr.reduce((r, o) => {

  const key = o.shape + '-' + o.color;



  const item = r.get(key) || Object.assign({}, o, {

    used: 0,

    instances: 0

  });



  item.used += o.used;

  item.instances += o.instances;



  return r.set(key, item);

}, new Map).values()];



console.log(result);