The art of combining arrays of objects while eliminating duplicates

Question

The art of combining arrays of objects while eliminating duplicates

I am in need of a solution to compare two object arrays, remove duplicates, and merge them into a single array. Although I am relatively new to javascript/Typescript, I have come across some blogs suggesting the use of Map, reduce, and filter methods for this task. Is that the most effective approach?

Alternatively, I am curious if creating a map and utilizing Map.ContainsKey or Map.getValues() could also achieve the desired result.

In reality, the objects within the arrays are quite extensive, with multiple keys and hundreds of records in each array.

   [
    {
        Name: Roger
        Country : Spain
    },
    {
        Name: Tiger
        Counry : USA
    },
    {
        Name: Micheal
        Country: USA
    },
]


[
    {
        Name: Sachin
        Country : India
    },
    {
        Name: Roger
        Counry : Spain
    },
]

output 

[
    {
        Name: Roger
        Country : Spain
    },
    {
        Name: Tiger
        Counry : USA
    },
    {
        Name: Micheal
        Country: USA
    },
    {
        Name: Sachin
        Country : India
    }
]

javascript arrays

Answer 1

Answer №1

A possible solution is to use a hash table with the desired values as keys and then add elements that do not have a flag in the hash table.

var array1 = [{ Name: 'Roger', Country: 'Spain' }, { Name: 'Tiger', Counry: 'USA' }, { Name: 'Micheal', Country: 'USA' }],
    array2 = [{ Name: 'sachin', Country: 'India' }, { Name: 'Roger', Country: 'Spain' }],
    hash = Object.create(null),
    result = [array1, array2].reduce(function (r, a) {
        a.forEach(function (o) {
            var key = ['Name', 'Country'].map(k => o[k]).join('|');
            if (!hash[key]) {
                r.push(o);
                hash[key] = true;
            }
        });
        return r;
    }, []);

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 2

A possible solution is to use a hash table with the desired values as keys and then add elements that do not have a flag in the hash table.

var array1 = [{ Name: 'Roger', Country: 'Spain' }, { Name: 'Tiger', Counry: 'USA' }, { Name: 'Micheal', Country: 'USA' }],
    array2 = [{ Name: 'sachin', Country: 'India' }, { Name: 'Roger', Country: 'Spain' }],
    hash = Object.create(null),
    result = [array1, array2].reduce(function (r, a) {
        a.forEach(function (o) {
            var key = ['Name', 'Country'].map(k => o[k]).join('|');
            if (!hash[key]) {
                r.push(o);
                hash[key] = true;
            }
        });
        return r;
    }, []);

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 3

Answer №2

Here is an efficient ES6 solution that utilizes the map() and filter() methods.

Combining two arrays of objects while eliminating duplicate objects

let arr1 =    [
    {
        Name: 'Roger',
        Country : 'spain'
    },
    {
        Name:'Tiger',
        Country : 'USA'
    },
    {
        Name: 'Micheal',
        Country: 'USA'
    },
];
let arr2 = [
    {
        Name: 'sachin',
        Country : 'India'
    },
    {
        Name:'Roger',
        Country : 'Spain'
    },
]
let arr3 = [...arr1, ...arr2]

function mergeUniqueArray(arr, comp) {

  let unique = arr
    .map(item => item[comp])

     // store the keys of the unique objects
    .map((item, i, final) => final.indexOf(item) === i && i)

    // eliminate the duplicate keys & store unique objects
    .filter(item => arr[item]).map(item => arr[item]);
   return unique;
}

console.log(mergeUniqueArray(arr3,'Name'));

Answer 4

Here is an efficient ES6 solution that utilizes the map() and filter() methods.

Combining two arrays of objects while eliminating duplicate objects

let arr1 =    [
    {
        Name: 'Roger',
        Country : 'spain'
    },
    {
        Name:'Tiger',
        Country : 'USA'
    },
    {
        Name: 'Micheal',
        Country: 'USA'
    },
];
let arr2 = [
    {
        Name: 'sachin',
        Country : 'India'
    },
    {
        Name:'Roger',
        Country : 'Spain'
    },
]
let arr3 = [...arr1, ...arr2]

function mergeUniqueArray(arr, comp) {

  let unique = arr
    .map(item => item[comp])

     // store the keys of the unique objects
    .map((item, i, final) => final.indexOf(item) === i && i)

    // eliminate the duplicate keys & store unique objects
    .filter(item => arr[item]).map(item => arr[item]);
   return unique;
}

console.log(mergeUniqueArray(arr3,'Name'));

Answer 5

Answer №3

Check out this potential solution:

// Step 1: Merge the two arrays together.
const mergedItems = itemsList1.concat(itemsList2);

// Step 2: Transform the merged array into key/value pairs.
const keyValuePairs = mergedItems.map(item => [`${item.Name}:${item.Country}`, item]);

// Step 3: Utilize a Map to remove duplicates.
const mapOfItems = new Map(keyValuePairs);

// Step 4: Convert the unique values back into an array.
const finalResult = [...mapOfItems.values()];

Here are some important points about this method:

When combining arrays in step 1, the order matters! Items from itemsList2 will take precedence over those from itemsList1. This is crucial for situations where objects have additional properties beyond what's being compared.
If there's a possibility of collisions due to special characters like : in name/country combinations, consider modifying how you construct the entry keys.
The use of a Map with a hashtable implementation ensures efficient duplicate removal.
Since Map maintains input sequence, the resulting array will mirror the order of elements in the merged array while eliminating duplicates. To change the output order, sorting may be necessary.

Answer 6

Check out this potential solution:

// Step 1: Merge the two arrays together.
const mergedItems = itemsList1.concat(itemsList2);

// Step 2: Transform the merged array into key/value pairs.
const keyValuePairs = mergedItems.map(item => [`${item.Name}:${item.Country}`, item]);

// Step 3: Utilize a Map to remove duplicates.
const mapOfItems = new Map(keyValuePairs);

// Step 4: Convert the unique values back into an array.
const finalResult = [...mapOfItems.values()];

Here are some important points about this method:

When combining arrays in step 1, the order matters! Items from itemsList2 will take precedence over those from itemsList1. This is crucial for situations where objects have additional properties beyond what's being compared.
If there's a possibility of collisions due to special characters like : in name/country combinations, consider modifying how you construct the entry keys.
The use of a Map with a hashtable implementation ensures efficient duplicate removal.
Since Map maintains input sequence, the resulting array will mirror the order of elements in the merged array while eliminating duplicates. To change the output order, sorting may be necessary.

The art of combining arrays of objects while eliminating duplicates

Answer №1

Answer №2

Answer №3

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