How to Merge Two Arrays in JavaScript and De-Duplicate Items

How to merge two arrays in JavaScript and de-duplicate items

To just merge the arrays (without removing duplicates)

ES5 version use Array.concat:

var array1 = ["Vijendra", "Singh"];
var array2 = ["Singh", "Shakya"];

array1 = array1.concat(array2);

console.log(array1);

JavaScript - merge two arrays of objects and de-duplicate based on property value

Using a double for loop and splice you can do it like so:

for(var i = 0, l = origArr.length; i < l; i++) {
    for(var j = 0, ll = updatingArr.length; j < ll; j++) {
        if(origArr[i].name === updatingArr[j].name) {
            origArr.splice(i, 1, updatingArr[j]);
            break;
        }
    }
}

Example here

How to merge two arrays in JavaScript and de-duplicate items

To just merge the arrays (without removing duplicates)

ES5 version use Array.concat:

var array1 = ["Vijendra", "Singh"];
var array2 = ["Singh", "Shakya"];

array1 = array1.concat(array2);

console.log(array1);

Javascript: Merge Two Arrays of Objects, Only If Not Duplicate (Based on Specified Object Key)

You can create a set of IDs from initialData and this will make "check if ID is already in initial data" faster - O(1):

var initialData = [{

    'ID': 1,

    'FirstName': 'Sally'

  },

  {

    'ID': 2,

    'FirstName': 'Jim'

  },

  {

    'ID': 3,

    'FirstName': 'Bob'

  }

];

var newData = [{

    'ID': 2,

    'FirstName': 'Jim'

  },

  {

    'ID': 4,

    'FirstName': 'Tom'

  },

  {

    'ID': 5,

    'FirstName': 'George'

  }

];

var ids = new Set(initialData.map(d => d.ID));

var merged = [...initialData, ...newData.filter(d => !ids.has(d.ID))];

console.log(merged);

Concat multiple arrays into one array without duplicates

var a = ["1","2","3"]

  , b = ["3","4","5"]

  , c = ["4","5","6"]

  , d = [];

function newArray(x,y,z) {

  x.concat(y,z).forEach(item =>{

     if (d.indexOf(item) == -1) 

       d.push(item); 

  });

  return d;

}

console.log(newArray(a,b,c));

JavaScript - Merge two array by key and keep duplicates

You could take an object for grouping same sku and shift objects for keeping the same order fro merging.

const
    array1 = [{ sku: "35189424", price: 107800, isNew: false, name: "Product Title A" }, { sku: "62617802", price: 107800, isNew: false, name: "Product Title D" }, { sku: "GRP00437", price: 107800, isNew: false, name: "Product Title B" }, { sku: "62617802", price: 107800, isNew: false, name: "Product Title D" }, { sku: "35189432", price: 107800, isNew: false, name: "Product Title YZ" }],
    array2 = [{ sku: "35189424", Url: "https://......", rating: 2, status: 0 }, { sku: "62617802", Url: "https://......", rating: 5, status: 1 }, { sku: "GRP00437", Url: "https://......", rating: 2, status: 1 }, { sku: "35189432", Url: "https://......", rating: 3, status: 1 }, { sku: "62617802", Url: "https://......", rating: 5, status: 1 }],
    skus = array2.reduce((r, o) => ((r[o.sku] = r[o.sku] || []).push(o), r), { }),
    result = array1.map(o => ({ ...o, ...skus[o.sku].shift() }));

console.log(result);

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Combine two arrays In one without duplicates

You can easily achieve the result using Set and flat.

const mapedTopicsArray = [
  ["javascript", "reactjs"],
  ["Java", "reactjs"],
];

const topicsArrayMergedWithoutDuplicates  = [...new Set(mapedTopicsArray.flat())];
console.log(topicsArrayMergedWithoutDuplicates );

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