# normal array to multi-dimensional array

I know there's already answer for a similar question, but the outcome is not what I'm looking for.

I want to have [0,1,2,3,4,5,6,7,8] inserted into a multi-dimensional array like:

[0,3,6],[1,4,7],[2,5,8]

[0,1,2],[3,4,5],[6,7,8]

``````const toMatrix = (arr, width) =>
arr.reduce((rows, key, index) => (index % width == 0 ? rows.push([key])
: rows[rows.length-1].push(key)) && rows, []);
``````

Other than using for...loop, is there a shorter way to do it?

You can try this. I have used "Array.reduce" with "Object.values" to achieve this.

``````var arr = [0,1,2,3,4,5,6,7,8]

var toMatrix = (arr, width) => {

let gap = Math.ceil(arr.length/width)

return Object.values(arr.reduce((o,d,i) => (o[i%gap] = (o[i%gap] || []).concat(d), o), {}))
}

console.log(toMatrix(arr, 3))

console.log(toMatrix(arr, 2))``````

You could take a remainder with ttha actual index and push the value to the result set.

``````const
toMatrix = (array, width) => array.reduce((r, v, i) => {
(r[i % width] = r[i % width] || []).push(v);
return r;
}, []),
format = array => array.map(a => a.join(' '));

console.log(format(toMatrix([0, 1, 2, 3, 4, 5, 6, 7, 8], 2)));
console.log(format(toMatrix([0, 1, 2, 3, 4, 5, 6, 7, 8], 3)));
console.log(format(toMatrix([0, 1, 2, 3, 4, 5, 6, 7, 8], 4)));``````
``.as-console-wrapper { max-height: 100% !important; top: 0; }``

``````input =[0,1,2,3,4,5,6,7,8]

function divideInGroups (array, groupCount) {
return input.reduce((acc, curr, index)=> {
let group = index % groupCount;
if(!acc[group]) acc[group]=[];
acc[group].push(curr);
return acc
},[])
}

console.log("3 Groups", divideInGroups(input,3));
console.log("2 Groups", divideInGroups(input,2));
console.log("1 Groups",divideInGroups(input,1));
console.log("5 Groups",divideInGroups(input,5));``````

Although there are many solutions already posted for this but anyway I'm going to post mine as I think its readable, viable and according to the OP's use case.

``````const toMatrix = (arr, width) => arr.reduce((rows, key, index) => {
let chunkLength = Math.ceil(arr.length / width);
let rowIndex = Math.ceil(index % chunkLength);
rows[rowIndex] ? rows[rowIndex].push(key) : rows.push([key]);
return rows;
}, []);
``````

``````const arr = [0, 1, 2, 3, 4, 5, 6, 7, 8]
const toMatrix = (arr, width) => arr.reduce((rows, key, index) => {
let chunkLength = Math.ceil(arr.length / width);
let rowIndex = Math.ceil(index % chunkLength);
rows[rowIndex] ? rows[rowIndex].push(key) : rows.push([key]);
return rows;
}, []);

console.log(toMatrix(arr, 3));
console.log(toMatrix(arr, 2));
console.log(toMatrix(arr, 1));
console.log(toMatrix(arr, 4));
console.log(toMatrix(arr, 5));``````

If you wish, you can also try the below code.

``````function splitToArrays(arr, width=1) {
/**
* PARAMETERS:-
* 	   arr   : array of numbers (integers in this case)
* 	   width : number of elements in each sub array
*/

let newArr = [];
let times  = arr.length / width;

for(let i = 0; i < width; i++) // each iteration adds a new sub array to newArr
{
let step = 0;
for(let j = 0; j < times; j = j + 1) { // each iteration adds new element to sub array

if(j === 0) {
let item = arr[i + step]; // fetch item from array
newArr.push([item]);      // push item to new array
step += width;
continue; // continue with next iteration,
// skip the following statements
}

// else
let item = arr[i + step]; // 0, 3, 6 | 1, 4, 7
newArr[i].push(item);
step += width; // increment step's value by 3 in this case
}
}

// finally
return newArr;
}

function main() {
// test case
let a = [0, 1, 2, 3, 4, 5, 6, 7, 8];
let b = splitToArrays(a, 3); // 3 denotes number of elements inside sub arrays

console.log(a);
console.log(b);
}

main();

/*
[ 0, 1, 2, 3, 4, 5, 6, 7, 8 ]
[ [ 0, 3, 6 ], [ 1, 4, 7 ], [ 2, 5, 8 ] ]
*/``````