JavaScript: Convert a 1D array into a 2D array by a given size

Question

Doing a freeCodeCamp challenge called "Chunky Monkey". The objective is to create a function that takes two parameters: a 1D array and a number for size.

The array is to be split into a number of groups of the length size (up to that number), thus creating a 2D array.

In my first attempt, my code was:

function chunkArrayInGroups(arr, size) {
  var set = arr.length / size;
  var count = 0;
  set = Math.ceil(set); //ensure that an integer is obtained
  var array = [];
  for (var i = 0; i < set; i++) {
    array[i] = []; //ensure each element i is an array
    for (var j = 0; j < size; j++) {
      array[i][j] = arr[count]; //obtain values from passed array, arr
      count++;
    }
  }
  return array;
}

var result = chunkArrayInGroups(["a", "b", "c", "d"], 2);
console.log(result);

I have traced this code a few times, but I cannot tell why it is wrong. Can someone please spot the error in it?

I eventually tackled the problem using a slightly different method, and it worked, but I am very interested in why the code above did not work.

i think the problem here is it always creates an array with the specified length. So when you call chunkArrayInGroups(["a", "b", "c", "d"], 2), you get [["a", "b", "c" ],["d", undefined,undefined]] — xGeo
– xGeo, Commented Jun 27, 2017 at 6:19
If chunkArrayInGroups(["a", "b", "c", "d", "e"], 2);, what is the expected result? [["a", "b"],["c", "d"],["e", undefined]] or [["a", "b"],["c", "d"],["e"]]? — shaochuancs
– shaochuancs, Commented Jun 27, 2017 at 6:19
It seems to only work some of the times, for example, it failed this test among others: chunkArrayInGroups([0, 1, 2, 3, 4, 5, 6, 7, 8], 4) should return [[0, 1, 2, 3], [4, 5, 6, 7], [8]]. — Matt
– Matt, Commented Jun 27, 2017 at 6:20

shaochuancs · Accepted Answer · 2017-06-27 06:21:44Z

1

You need to break the loop once count reach the max limit:

function chunkArrayInGroups(arr, size) {
  var set = arr.length/size; 
  var count = 0; 
  set = Math.ceil(set); //ensure that an integer is obtained
  var array = []; 
  out:
  for(var i = 0; i<set; i++){
    array[i] = []; //ensure each element i is an array
    for (var j=0; j<size; j++){
      if (count === arr.length) {
        break out;
      }
      array[i][j] = arr[count]; //obtain values from passed array, arr
      count++; 
    }
  }      
  return array;
}

var result = chunkArrayInGroups([0, 1, 2, 3, 4, 5, 6, 7, 8], 4);

console.log(result);

answered Jun 27, 2017 at 6:21

shaochuancs

16.4k3 gold badges63 silver badges68 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

f1ames · Accepted Answer · 2017-06-27 06:26:33Z

The code is working (with some exceptions, see result of console.log( chunkArrayInGroups(["a", "b", "c", "d"], 5) ); and @shaochuancs answer), but you may try a simpler approach utilizing native methods, like (see chunk function):

function chunkArrayInGroups(arr, size) {
  var set = arr.length/size; 
  var count = 0; 
  set = Math.ceil(set); //ensure that an integer is obtained
  var array = []; 
  for(var i = 0; i<set; i++){
    array[i] = []; //ensure each element i is an array
    for (var j=0; j<size; j++){
      array[i][j] = arr[count]; //obtain values from passed array, arr
      count++; 
    }
  }      
  return array;
}

function chunk( arr, size ) {
  var chunkedArray = [];
  while ( arr.length > 0 ) {
    chunkedArray.push( arr.splice( 0, size ) );
  }
  return chunkedArray;
}

console.log( chunkArrayInGroups(["a", "b", "c", "d"], 2) );
console.log( chunkArrayInGroups(["a", "b", "c", "d"], 5) );
console.log( chunkArrayInGroups([], 2) );

console.log( chunk(["a", "b", "c", "d"], 2) );
console.log( chunk(["a", "b", "c", "d"], 5) );
console.log( chunk([], 2) );

Collectives™ on Stack Overflow

JavaScript: Convert a 1D array into a 2D array by a given size

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related