JavaScript Program to Remove Duplicates From Array

In this example, you will learn to write a JavaScript program that removes duplicate value from an array.

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


Example 1: Using indexOf() and push()

// program to remove duplicate value from an array

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

let array = [1, 2, 3, 2, 3];

// calling the function
// passing array argument
getUnique(array);

Output

[1, 2, 3]

In the above program, the duplicate elements are removed from array.

Here,

  • The for...of loop is used to loop through all the elements of an arr array.
  • 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 uniqueArr using push().

Example 2: Using Set

// program to remove duplicate value from an array

function getUnique(arr){

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

    console.log(uniqueArr);
}

let array = [1, 2, 3, 2, 3];

// calling the function
getUnique(array);

Output

[1, 2, 3]

In the above program, Set is used to remove duplicate items from an array.

A Set is a collection of unique values.

Here,

  • The array is converted to Set and all the duplicate elements are automatically removed.
  • The spread syntax ... is used to include all the elements of the Set to a new array.