JS Program to Remove Duplicates From Array

solution1

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

let uniqueArray = [];
array.forEach((c) => {
    if (!uniqueArray.includes(c)) {
        uniqueArray.push(c);
    }
});

console.log(uniqueArray);

solution2

function getUnique(arr){

    let uniqueArr = [];

    //loop through array 
    for(let i of arr) {
        if(uniqueArr.indexOf(i) === -1) {
            uniqueArr.push(i);
        }
    }
    console.log(uniqueArr);
}
const array = [1,2,3,2,3];

solution3

let array = ['1', '2', '3', '2', '3'];
let uniqueArray = [...new Set(array)];

console.log(uniqueArray);

Comments

[Mike Talbot ⭐]

Both of these solutions are exponentially slow due to the need to search the growing unique array (includes and indexOf do a linear search). You can do the unique array in O(N) using a Set, Map or in this case a PoJo. The one liner using Set is:

    const uniqueArr = [...new Set(array)]

[JoelBonetR 🥇]

To add context here for learning purposes, a POJO is an object that only contains data (as opposed to methods or internal state), most JavaScript codebases consider objects created using curly braces {} to be POJOs, however, more strict codebases sometimes create POJOs by calling Object.create(null) to avoid inheriting from the built-in Object class.

JavaScript Maps are an alternative to POJOs for storing data because they neither inherit keys from the Object class.

A downside is that objects are generally easier to work with than maps cause not all JS functions, frameworks, and libs support maps.
i.e. JSON.stringify() function doesn't serialize maps by default:

const map = new Map([['score', 256, 'stage', 3]]);
JSON.stringify(map); // '{}'

[hannaA]

Best friends are options kk thanks

[Ivan Jeremic]

People should better lern how to use JavaScript Set() instead of using arrays which need to be unique.

[hannaA]

So which solution are you using to Remove Duplicates From Array?

[Ivan Jeremic]

Set() does not allow duplicates in the first place so there is no need for me to remove duplicates just use Set from the beginning when it need to be unique.

[hannaA]

It's a good suggestion if you care about the performance.

[bap]

The best solution of above is solution3, but i suggest a new solution if didn't know about Set
Create a new object and create a new key with value true if you loop in array and it not existed, so if it not you will get the undefined value