What is best approach to remove duplicate values from an array in native javascript

Question

I have an array in javascript like this

var arr = [1,2,1.5,3,1.5,1];

I want to remove all duplicate values from the array,So my output will be like

[2,3]

I can do it using loops.I have posted this question here because I need a fasted way to get it done.

Not sure if its the *best approach* but you could use a set: `console.log([...new Set(arr)])` — Nick Parsons, Nov 30 '18 at 09:57
@Luke that is not a duplicate since OP wants to get only the values that occurs once instead of getting the unique values — Andreas, Nov 30 '18 at 09:57
A valid (and often used) downvote reason is "The question shows no research effort". You did not show visible effort to come up with a solution yourself, by means of a code sample or by linking to similar questions that have not helped you. — Peter B, Nov 30 '18 at 10:14
Dear @peterB if you read question i have also mentioned : I can do it using loops.I have posted this question here because I need a fasted way to get it done. — Shakti S, Nov 30 '18 at 10:24

score 8 · Answer 1 · edited Jun 20 '20 at 09:12

You could check the first and last index of the value and take it if the index is the same.

var array = [1, 2, 1.5, 3, 1.5, 1],
    ones = array.filter((v, _, a) => a.indexOf(v) === a.lastIndexOf(v));

console.log(ones);

An approach with a Map.

It works with a map by taking the opposite of the check if the map has already one entry with the given value.

For any following same values, the entry changes to false, which later omits these values.

var array = [1, 2, 1.5, 3, 1.5, 1, 1, 1],
    map = array.reduce((m, v) => m.set(v, !m.has(v)), new Map),
    ones = array.filter(Map.prototype.get, map);

console.log(ones);
console.log([...map]); // just for checking the values

Nitish Narang · Accepted Answer · 2018-11-30T10:51:25.903

1

I tried this new approach to get only non-repeated values using just Array.filter... Fellow users comments are welcome if you feel it's better performance wise or not.

var arr = [1,2,1.5,3,1.5,1]

let tmp = {}
let res = [...arr, ...arr].filter((d, i) => {
  tmp[d] = (tmp[d] || 0) + 1
  return i > arr.length - 1 && tmp[d] == 2
})

console.log(res)

edited Nov 30 '18 at 10:51

answered Nov 30 '18 at 10:36

Nitish Narang

4,124
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that is just an approach to try to get a single loop solution, which is not, because of the doubeling of the items and the late use if the filtering for the second half of the new array, while you use the first to count the items. it looks more complicated than it should be. – Nina Scholz Nov 30 '18 at 15:01

score 0 · Answer 3 · answered Nov 30 '18 at 10:38

0

We can achieve this using JavaScripts .filter() method.

const arr = [1,2,1.5,3,1.5,1];

const newArr = arr.filter(val => (arr.filter(v => v === val).length === 1));

console.log(newArr); // [ 2, 3 ]

answered Nov 30 '18 at 10:38

Benni Russell

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What is best approach to remove duplicate values from an array in native javascript

3 Answers3