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

function matrixify( source, count )
{
    var matrixified = [];
    var tmp;
    // iterate through the source array
    for( var i = 0; i < source.length; i++ )
    {
        // use modulous to make sure you have the correct length.
        if( i % count == 0 )
        {
            // if tmp exists, push it to the return array
            if( tmp && tmp.length ) matrixified.push(tmp);
            // reset the temporary array
            tmp = [];
        }
        // add the current source value to the temp array.
        tmp.push(source[i])
    }
    // return the result
    return matrixified;
}

If you want to actually replace an array's internal values, I believe you can call the following:

source.splice(0, source.length, matrixify(source,3));

Answer 2

function chunkArrToMultiDimArr(arr, size) {

    var newArray = [];

    while(arr.length > 0)
    {
      newArray.push(arr.slice(0, size));
      arr = arr.slice(size);
    }

  return newArray;
}

//example - call function
chunkArrToMultiDimArr(["a", "b", "c", "d"], 2);

Answer 3

You can use the Array.prototype.reduce function to do this in one line.

ECMAScript 6 style:

myArr.reduce((rows, key, index) => (index % 3 == 0 ? rows.push([key]) 
  : rows[rows.length-1].push(key)) && rows, []);

"Normal" JavaScript:

myArr.reduce(function (rows, key, index) { 
  return (index % 3 == 0 ? rows.push([key]) 
    : rows[rows.length-1].push(key)) && rows;
}, []);

You can change the 3 to whatever you want the number of columns to be, or better yet, put it in a reusable function:

ECMAScript 6 style:

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

"Normal" JavaScript:

function toMatrix(arr, width) {
  return arr.reduce(function (rows, key, index) { 
    return (index % width == 0 ? rows.push([key]) 
      : rows[rows.length-1].push(key)) && rows;
  }, []);
}