How to remove duplicate values from JS array?

Another very common situation is to remove repeated values from an array.

Let’s show some of the approaches you can use:

Removing duplicate values from JS array using the Set constructor and the spread syntax

The Set object lets you store unique values of any type, whether primitive values or object references.

const arr = ["a", 2, "c", 4, "a", 2, 2, 5, "c"];
const set1 = new Set(arr);

const result1 = [...set1.values()];
console.log(result1);
//[ 'a', 2, 'c', 4, 5 ]

const result2 = [...new Set(arr)];
console.log(result2);
//[ 'a', 2, 'c', 4, 5 ]

Removing duplicate values from JS array using filter()

We just go over the array and verify if the starting position of each element in the array is identical to the current position for each element. For duplicate items, these two locations are obviously different.

const arr = ["a", 2, "c", 4, "a", 2, 2, 5, "c"];

const filtered = arr.filter((item, index) => arr.indexOf(item) === index);

console.log(filtered);

//[ 'a', 2, 'c', 4, 5 ]

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