How to convert simple array into two-dimensional array (matrix) with Javascript

Question

Imagine I have an array:

A = Array(1, 2, 3, 4, 5, 6, 7, 8, 9);

And I want it to convert into 2-dimensional array (matrix of N x M), for ins

Answer 1

The cleanest way I could come up with when stumbling across this myself was the following:

const arrayToMatrix = (array, columns) => Array(Math.ceil(array.length / columns)).fill('').reduce((acc, cur, index) => {
  return [...acc, [...array].splice(index * columns, columns)]
}, [])

where usage would be something like

const things = [
  'item 1', 'item 2',
  'item 1', 'item 2',
  'item 1', 'item 2'
]

const result = arrayToMatrix(things, 2)

where result ends up being

[
  ['item 1', 'item 2'],
  ['item 1', 'item 2'],
  ['item 1', 'item 2']
]

Answer 2

Simplest way with ES6 using Array.from()

const matrixify = (arr, size) => 
Array.from({ length: Math.ceil(arr.length / size) }, (v, i) =>  
arr.slice(i * size, i * size + size));
const list =  [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12] ;
console.log(matrixify(list, 3));

Answer 3

Simply use two for loops:

var rowNum = 3;
var colNum = 3;
var k = 0;
var dest = new Array(rowNum);

for (i=0; i<rowNum; ++i) {
  var tmp = new Array(colNum);
  for (j=0; j<colNum; ++j) {
    tmp[j] = src[k];
    k++;
  }
  dest[i] = tmp;
}

Answer 4

you can use push and slice like this

var array = [1,2,3,4,5,6,7,8,9] ;
var newarray = [[],[]] ;
newarray[0].push(array) ;
console.log(newarray[0]) ;

output will be

[[1, 2, 3, 4, 5, 6, 7, 8, 9]]

if you want divide array into 3 array

var array = [1,2,3,4,5,6,7,8,9] ;
var newarray = [[],[]] ;
newarray[0].push(array.slice(0,2)) ;
newarray[1].push(array.slice(3,5)) ;
newarray[2].push(array.slice(6,8)) ;

instead of three lines you can use splice

while(array.length) newarray.push(array.splice(0,3));

Answer 5

This a simple way to convert an array to a two-dimensional array, especially when you want to manipulate array items generated.

const arr = [1,2,3,4,5,6,7,8,9]
let i = 0;
let twoDimension = [];
while (i < arr.length) {
  const first = arr[i];
  const second = arr[i + 1];
  const third = arr[i + 2]
  let tempArr = []

  if (first && second && third) {
    tempArr.push(first, second, third)
  } else if (first && second) {
    tempArr.push(first, second)
  } else {
    tempArr.push(first)
  }

  twoDimension[twoDimension.length] = tempArr;
  i += 3;
 }
 console.log(twoDimension)

Answer 6

Short answer use:

const gridArray=(a,b)=>{const d=[];return a.forEach((e,f)=>{const 
h=Math.floor(f/b);d[h]=d[h]||[],d[h][f%b]=a[f]}),d};

Where:

a: is the array
b: is the number of columns

Long answer you can read the article:

How to convert an array of length ‘n’ to array grid