[рони]

Роман1479,

var matrix4D = [
  1, 1, 1, 1,
  1, 1, 1, 1,
  1, 1, 1, 1,
  1, 1, 1, 1
];
var matrix4_D = [
  1, 1, 1, 3,
  1, 1, 6, 1,
  1, 2, 1, 10,
  9, 1, 1, 1,
  1, 1, 11, 1
];


var matrix5D = [
  1, 2, 3, 4, 5,
  1, 1, 1, 3, 4,
  1, 1, 1, 1, 1
];

function function_matrix(arr, num){
    var l = Math.min(num, arr.length/num)
    var n = --num;
    var res = [];

    for (var i = 0; i < l; i++) {
        res.push(arr[n])
        n += num
    }
    return res
}
alert(function_matrix(matrix4D, 4));
alert(function_matrix(matrix4_D, 4));
alert(function_matrix(matrix5D, 5));