Array.from(new Set([1,2,3,3,4,4]))    // [1,2,3,4]

[...new Set([1,2,3,3,4,4])]        // [1,2,3,4]

Array.prototype.distinct = function() {

    const map = {}

    const result = []

    for (const n of this) {

        if (!(n in map)) {

            map[n] = 1

            result.push(n)

        }

    }

    return result

}

[1,2,3,3,4,4].distinct(); //[1,2,3,4]