在对象数组中查找重复值并合并一些重复的键和值

Question

我有两个对象数组

array = [
 {
  "id_0":356,
  "name":"India",
  "key1":150
 },
 {
  "id_0":356,
  "name":"India",
  "key2":200
 },
 {
  "id_0":748,
  "name":"Swaziland",
  "key1":140
 },
 {
  "id_0":748,
  "name":"Swaziland",
  "key2":180
 }
]

我正在尝试在对象数组中查找重复的id_0，并将key2 的重复对象和值合并。

我希望结果是：

array = [
 {
  "id_0":356,
  "name":"India",
  "key1":150,
  "key2":200
 },
 {
  "id_0":748,
  "name":"Swaziland",
  "key1":140,
  "key2":180
 }
]

如何找到重复值并将重复的键和值合并到数组中？

Answer 1

您可以根据需要使用Array.prototype.reduce() 来减少您的阵列。

可以使用Object.assign()合并重复项。

var array = [
    { 'id_0': 356, 'name': 'India', 'key1': 150 },
    { 'id_0': 356, 'name': 'India', 'key2': 200 }
];

var result = array.reduce(function(prev, item) {
    var newItem = prev.find(function(i) {
        return i.id_0 === item.id_0; 
    });
    if (newItem) {
        Object.assign(newItem, item);
    } else {
        prev.push(item);
    }
    return prev;
}, []);

console.log(result);

Object.assign 是 ES6 的一部分。如果它不适合您，只需将其替换为：

for (var attrname in item) {
    newItem[attrname] = item[attrname];
};

Answer 2

试试这个fiddle

var array = [
 {
  "id_0":356,
  "name":"India",
  "key1":150
 },
 {
  "id_0":356,
  "name":"India",
  "key2":200
 },
 {
  "id_0":356,
  "name2":"china",
  "key2":200
 }
]
function mergeArray( arr )
{
   var outputObj = {};
   for ( var counter = 0; counter < arr.length; counter++ )
   {
      var obj = arr[ counter ];
      for( var key in obj )
      {
         if ( !outputObj[ key ] )
         {
           outputObj[ key ] = obj[ key ];
         }
      }
   }
   return outputObj;
}
console.log( mergeArray( array ) );

编辑 fiddle 以满足您的“更新”要求

var array = [
 {
  "id_0":356,
  "name":"India",
  "key1":150
 },
 {
  "id_0":356,
  "name":"India",
  "key2":200
 },
 {
  "id_0":400,
  "name2":"china",
  "key2":200
 },
 {
  "id_0":400,
  "name2":"china",
  "key2":200
 }
]
function mergeArray( arr )
{
   var outputObj = {};
   for ( var counter = 0; counter < arr.length; counter++ )
   {
      var obj = arr[ counter ];
      for( var key in obj )
      {
         if ( !outputObj[ key ] )
         {
           outputObj[ key ] = obj[ key ];
         }
      }
   }
   return outputObj;
}
function collateArray( arr )
{
   var outputObj = {};
   var result = [];
   for ( var counter = 0; counter < arr.length; counter++ )
   {
      var obj = arr[ counter ];
      var id_0value = obj[ "id_0" ];
      if ( !outputObj[ id_0value ] )
      {
        outputObj[ id_0value ] = [];
      }
      outputObj[ id_0value ].push( obj );
   }
   console.log( outputObj );
   for ( var key in outputObj )
   {
      result.push( mergeArray( outputObj[ key ] ) );
   }
   return result;

}
console.log( collateArray( array ) );

Answer 3

使用一个临时的Object作为存储key => item的映射可以使时间复杂度达到O(n)：

var arr = [
 {
  "id_0":356,
  "name":"India",
  "key1":150
 },
 {
  "id_0":356,
  "name":"India",
  "key2":200
 },
 {
  "id_0":748,
  "name":"Swaziland",
  "key1":140
 },
 {
  "id_0":748,
  "name":"Swaziland",
  "key2":180
 }
];

// items:            the array to be merged to unique.
// attrName:    the attribute's name that is for distinguish,
// isOverwrite:decides whether the value will be overwrite by later ones or not. Default to false. 
function getUnique(items, attrName, isOverwrite) {
  // Map to keep reference to objects by its id.
  var store = {};
  // The array for output result.
  var result = [];
  
  isOverwrite = !!isOverwrite;
  
  items.forEach(function(item) {
    var id = item[attrName];
    var key;
    
    // Try to fetch item by id from store.
    var target = store[id];
    
    // If target item exist in store, its dulplicated, we need to merge it.
    if (typeof target !== 'undefined') {
      // If it's presented, we need to merge it into existing one.
      for (key in item) {
        if (!item.hasOwnProperty(key)) {
          continue;
        }
        
        // If isOverwrite is true, always use the newest value, otherwise,
        // we only apply values that are not exist in target yet.
        if (isOverwrite || typeof target[key] === 'undefined') {
          target[key] = item[key];
        }
      }
    } else {
      // If its not in store yet, put it a clone into result, and to map for 
      // later reference.
      var clone = {};
      for (key in item) {
        if (item.hasOwnProperty(key)) {
          clone[key] = item[key];
        }        
      }
      store[id] = clone;      
      // Also put it into the result array.
      result.push(clone);
   }
  });

  return result;
}

console.log(getUnique(arr, 'id_0'));