JavaScript Program to Merge Two Arrays and Remove Duplicate Items

In this example, you will learn to write a JavaScript program that will merge two arrays and remove duplicate items from an array.

To understand this example, you should have the knowledge of the following JavaScript programming topics:


Example 1: Using concat() and for Loop

// program to merge and remove duplicate value from an array

function getUniqueAfterMerge(arr1, arr2){

    // merge two arrays
    let arr = arr1.concat(arr2);
    let uniqueArr = [];

    // loop through array
    for(let i of arr) {
        if(uniqueArr.indexOf(i) === -1) {
            uniqueArr.push(i);
        }
    }
    console.log(uniqueArr);
}

let array1 = [1, 2, 3];
let array2 = [2, 3, 5]

// calling the function
// passing array argument
getUniqueAfterMerge(array1, array2);

Output

[1, 2, 3, 5]

In the above program, the two array elements are merged together and the duplicate elements are removed.

Here,

  • The two arrays are merged using the concat() method.
  • The for...of loop is used to loop through all the elements of arr.
  • The indexOf() method returns -1 if the element is not in the array.

Hence, during each iteration, if the element equals -1, the element is added to a uniqueArr array using the push() method.


Example 2: Using Spread Syntax and Set

// program to merge and remove duplicate value from an array

function getUniqueAfterMerge(arr1, arr2){

    // merge two arrays
    let arr = [...arr1, ...arr2];

    // removing duplicate
    let uniqueArr = [...new Set(arr)];

    console.log(uniqueArr);
}

let array1 = [1, 2, 3];
let array2 = [2, 3, 5]

// calling the function
getUniqueAfterMerge(array1, array2);

Output

[1, 2, 3, 5]

In the above program, two arrays are merged together and Set is used to remove duplicate items from an array.

The Set is a collection of unique values.

Here,

  • Two array elements are merged together using the spread syntax ...
  • The array is converted to Set and all the duplicate elements are automatically removed..
  • The spread syntax ... is then used to include all the elements of the set back to an array.