normal array to multi-dimensional array

user_186887 0
Viewed 82

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]

instead of:

[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?

multidimensional-array javascript
5 Answers

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; }

user_14476750

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))

user_30484290 

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));

user_55802400

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));

user_82695810

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 ] ]
*/

user_66151630
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