How to remove duplicates element from array

In this post i'm going to remove duplicates element from array,i will try with multiple approaches to remove duplicates element from array.

Method 1
Using Set

const array = ["a","b","c","d","a","c","e","f"];
const m1 = [...new Set(array)];
console.log(m1);
// ["a", "b", "c", "d", "e", "f"] 

Method 2
Using object

const array = ["a","b","c","d","a","c","e","f"];
let obj = {};
for (let arr of array){
obj[arr]=true;
}
console.log(Object.keys(obj));
// ["a", "b", "c", "d", "e", "f"] 

Method 3
Using Loop

const array = ["a","b","c","d","a","c","e","f"];
const m3 = [];
for(var i = 0;i<array.length;i++){
const arr = array[i];
m3.indexOf(arr) === -1 && m3.push(arr);
}
console.log(m3)
// ["a", "b", "c", "d", "e", "f"]

Method 4
Using Filter

const array = ["a","b","c","d","a","c","e","f"];
const m4 = array.filter((el,index)=>array.indexOf(el) == index);
console.log(m4);
// ["a", "b", "c", "d", "e", "f"]

Comments

[Jon Randy 🎖️]

Another 'using object' one with reduce:

const array = ["a","b","c","d","a","c","e","f"];
console.log(Object.keys(array.reduce((a,v)=>({...a,[v]:1}),{})));

[Abu Jaid]

yeah great !

[Yair Even Or]

Best answer:

stackoverflow.com/a/1838755/104380

[Ghaleb]

Not even close.

For starters, it does not solve the proposed problem (filtering out duplicates); it returns the list of nonunique items.

Second, the time complexity of that solution is $O(n^2)$ . For an array of size $n$ , the filter function needs to run $(n - i)$ iterations for each element at index $i$ .

Even if the goal is to return the list of nonunique items - which, again, is not the case here - a solution with $O(n^2)$ time complexity is most definitely not the "best".