# Extract subarray of Columns from a multidimensional array and mutate the original array to remove those columns JavaScript

I want to extract a subarray of `Columns` from a multidimensional array and mutate the original array to remove those columns in JavaScript

Ex: If I have an array

``````originalArray =
[
[A, B, C, D, E, F],
[a1,b1,c1,d1,e1,f1],
[a2,b2,c2,d2,e2,f2],
[a3,b3,c3,d3,e3,f3]
[
``````

Where `A,B,C,D,E,F` are headers
and I want to extract columns [4,0,3] in this order I would get

``````subArray =
[
[E, A, D],
[e1,a1,d1],
[e2,a2,d2],
[e3,a3,d3]
[

originalArray =
[
[B, C, F],
[b1,c1,f1],
[b2,c2,f2],
[b3,c3,f3]
[
``````

which does this for rows

``````let subArray = originalArray.reduce((accumulator, current, index) => {
if (idxList.includes(index)) {
//if the current index is included in the idxList array,
//push the current value to the accumulator
accumulator.push(current);
} else {
//push the current value to the `tempArray`.
tempArray.push(current)
}
return accumulator;
}, []);
``````

Then I will concatenate these two arrays

reorderedArray = […subArray, …originalArray]

Reduce seems like an interesting approach and it seems like it should be a simple fix but I have to admit I am having a hard time understanding `Reduce`

### >Solution :

You could add the missing indices to `order` and map the array by mapping nested array with the indices of order.

``````let
data = [['A', 'B', 'C', 'D', 'E', 'F'], ['a1', 'b1', 'c1', 'd1', 'e1', 'f1'], ['a2', 'b2', 'c2', 'd2', 'e2', 'f2'], ['a3', 'b3', 'c3', 'd3', 'e3', 'f3']],
order = [4, 0, 3],
seen = new Set(order),
i = 0;

while (order.length < data.length) {
while (seen.has(i)) ++i;
order.push(i++);
}

data = data.map(a => order.map(i => a[i]));

data.forEach(a => console.log(...a));``````