Discover identical values within an array of objects and consolidate certain duplicate keys and values

Question

Discover identical values within an array of objects and consolidate certain duplicate keys and values

I have two lists of items

list1 = [
 {
  "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
 }
]

I am attempting to identify the matching id_0 in the list and combine the duplicate item's key2 and its value.

The desired outcome is as follows:

list1 = [
 {
  "id_0":356,
  "name":"India",
  "key1":150,
  "key2":200
 },
 {
  "id_0":748,
  "name":"Swaziland",
  "key1":140,
  "key2":180
 }
]

What is the process to locate the duplicate value and merge the repeated key-value pair in the list?

javascript arrays

Answer 1

Answer №1

To streamline your array, employ the Array.prototype.reduce() method.

Combine duplicate items by utilizing Object.assign().

var data = [
    { 'id_1': 789, 'title': 'USA', 'value1': 300 },
    { 'id_1': 789, 'title': 'USA', 'value2': 400 }
];

var outcome = data.reduce(function(previous, element) {
    var newElement = previous.find(function(i) {
        return i.id_1 === element.id_1; 
    });
    if (newElement) {
        Object.assign(newElement, element);
    } else {
        previous.push(element);
    }
    return previous;
}, []);

console.log(outcome);

If Object.assign from ES6 is not functioning properly, you can substitute it with:

for (var property in element) {
    newElement[property] = element[property];
};

Answer 2

To streamline your array, employ the Array.prototype.reduce() method.

Combine duplicate items by utilizing Object.assign().

var data = [
    { 'id_1': 789, 'title': 'USA', 'value1': 300 },
    { 'id_1': 789, 'title': 'USA', 'value2': 400 }
];

var outcome = data.reduce(function(previous, element) {
    var newElement = previous.find(function(i) {
        return i.id_1 === element.id_1; 
    });
    if (newElement) {
        Object.assign(newElement, element);
    } else {
        previous.push(element);
    }
    return previous;
}, []);

console.log(outcome);

If Object.assign from ES6 is not functioning properly, you can substitute it with:

for (var property in element) {
    newElement[property] = element[property];
};

Answer 3

Answer №2

Check out this JSFiddle link

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 ) );

For an 'UPDATED' version, click on this updated fiddle link

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 4

Check out this JSFiddle link

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 ) );

For an 'UPDATED' version, click on this updated fiddle link

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 5

Answer №3

To achieve a time complexity of O(n), using a temporary Object as a map to store key => item is recommended:

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 into unique values.
// attrName:    the attribute's name used for distinguishing items.
// isOverwrite:Determines if values should be overwritten by later ones or not. Default is false.
function getUnique(items, attrName, isOverwrite) {
  // Map to store objects based on their id.
  var store = {};
  // Array to hold the result.
  var result = [];
  
  isOverwrite = !!isOverwrite;
  
  items.forEach(function(item) {
    var id = item[attrName];
    var key;
    
    // Check if item already exists in store.
    var target = store[id];
    
    // If item exists in store, merge it with existing one.
    if (typeof target !== 'undefined') {
      for (key in item) {
        if (!item.hasOwnProperty(key)) {
          continue;
        }
        
        // Use newest value if isOverwrite is true, apply only new values otherwise.
        if (isOverwrite || typeof target[key] === 'undefined') {
          target[key] = item[key];
        }
      }
    } else {
      // If item is not in store yet, clone it and put in result array and map for reference.
      var clone = {};
      for (key in item) {
        if (item.hasOwnProperty(key)) {
          clone[key] = item[key];
        }        
      }
      store[id] = clone;      
      result.push(clone);
   }
  });

  return result;
}

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

Answer 6

To achieve a time complexity of O(n), using a temporary Object as a map to store key => item is recommended:

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 into unique values.
// attrName:    the attribute's name used for distinguishing items.
// isOverwrite:Determines if values should be overwritten by later ones or not. Default is false.
function getUnique(items, attrName, isOverwrite) {
  // Map to store objects based on their id.
  var store = {};
  // Array to hold the result.
  var result = [];
  
  isOverwrite = !!isOverwrite;
  
  items.forEach(function(item) {
    var id = item[attrName];
    var key;
    
    // Check if item already exists in store.
    var target = store[id];
    
    // If item exists in store, merge it with existing one.
    if (typeof target !== 'undefined') {
      for (key in item) {
        if (!item.hasOwnProperty(key)) {
          continue;
        }
        
        // Use newest value if isOverwrite is true, apply only new values otherwise.
        if (isOverwrite || typeof target[key] === 'undefined') {
          target[key] = item[key];
        }
      }
    } else {
      // If item is not in store yet, clone it and put in result array and map for reference.
      var clone = {};
      for (key in item) {
        if (item.hasOwnProperty(key)) {
          clone[key] = item[key];
        }        
      }
      store[id] = clone;      
      result.push(clone);
   }
  });

  return result;
}

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

Discover identical values within an array of objects and consolidate certain duplicate keys and values

Answer №1

Answer №2

Answer №3

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