A routine to print all arrangements of the given numbers in an array avoiding duplicates.

permutations.js

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

const swap = (i, j) => {
    const temp = arr[i];
    arr[i] = arr[j];
    arr[j] = temp;
}

const print = () => {
    console.log(arr);
}

const permutate = (start) => {
    if (start == arr.length) {
        print();
        return;
    }
    permutate(start+1);
    for (let i= start+1; i < arr.length; i++) {
        if (arr.slice(start, i).indexOf(arr[i]) != -1) continue;
        swap(start, i);
        permutate(start+1);
        swap(i, start);
    }
}

permutate(0);