Discussion on: Removing duplicates from an array

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Nice article. :)

I guess on a daily basis I would go with Set approach for simplicity. I just wanted to add that in a interview I would probably try to come up with an O(n) solution, so something like:

function removeDuplicates(arr){
    let map = {};

    return arr.reduce((acc, curr) => {
        if(!map[curr]){
            map[curr] = true;
            return [...acc, curr];
        } else {
            return acc;
        }
    }, []);
}

Oliver Anteros • Dec 8 '19 • Edited

const removeDouplicate = (arr) => 
    Object.keys(
        arr.reduce((res, val) => ({
            ...res, 
            [val]: true
        }, {})
    );

Regarding comments about returning a string array independent of the input data:

const removeDouplicate = (arr) => 
    Object.entries(
        arr.reduce((res, val) => ({
            ...res, 
            [val]: val
        }, {})
    ).map(([_, val]) => val);

Regarding comments about creating N number of objects:

const removeDouplicate = (arr) => 
    Object.entries(
        arr.reduce((res, val) => (
            res[val] = val,
            res
        ), {})
    ).map(([_, val]) => val);

This will work for all arrays as long as they only contain primitive values. Seeing as res[{ foo: 42 }] will access the index res['[object Object]'] no matter the object.

Charles Assunção • Dec 9 '19

Yeah, fthis works but you are "mutating" the data itself