javascript - 通过相同的键组合多个数组

Question

这个问题已经有答案了:

Combining JavaScript objects in an array with same key value (4 个回答)

已关闭 6 年前。

我正在尝试按特定的 key 组合多个数组属性(property)。例如，我有

arr1

  [{
    key: 'A',
    items: [{name: 'a item'}]
  }, {
    key: 'B',
    items: [{name: 'b item'}]
  }]

arr2

  [{
    key: 'B',
    items: [{name: 'another b item'}, {name: 'more b items'}, {name: 'even more b items'}]
  }]

如何生成以下arr3？

  [{
    key: 'A',
    items: [{name: 'a item'}]
  },
  {
    key: 'B',
    items: [{name: 'b item'}, {name: 'another b item'}, {name: 'more b items'}, {name: 'even more b items'}]
  }]

Answer 1

可以使用这样的哈希表:

arr1=[{
    key: 'A',
    items: [{name: 'a item'}]
  }, {
    key: 'B',
    items: [{name: 'b item'}]
  }];

arr2=[{
    key: 'B',
    items: [{name: 'another b item'}, {name: 'more b items'}, {name: 'even more b items'}]
  }];
  
console.log(arr1.concat(arr2).reduce((function(hash){
   return function(array,obj){
    if(!hash[obj.key])
     array.push(hash[obj.key]=obj);
    else
       hash[obj.key].items.push(...obj.items);
    return array;
   };    

})({}),[]));

一些解释:

arr1.concat(arr2)//just work with one array as its easier
.reduce(...,[]));//reduce this array to the resulting array
//through
(function(hash){//an IIFE to closure our hash object
...
})({})
//which evaluates to
  function(array,obj){//take the resulting array and one object of the input
    if(!hash[obj.key])//if we dont have the key yet
     array.push(hash[obj.key]=obj);//init the object and add to our result
    else
       hash[obj.key].items.push(...obj.items);//simply concat the items
    return array;
  };