Grouping arrays and 2D arrays into a single 2D array with the same length for all

The final result must always contain 6 values in each index:

[
   [value_1,value_2,value_3,value_4,value_5,value_6],
   [value_1,value_2,value_3,value_4,value_5,value_6]
]

Position of the values:

Possible arrays can be:

function if_empty(the_list) {
  if (the_list.length > 0) {
    return the_list
  } else {
    return [[null,null]]
  }
}

function group_arrays() {
  const menu = [
    ['abcd'],
    ['1234']
  ];

  const home_team = [];
  const ht = if_empty(home_team);

  const away_team = [
    ['val1', '0001'],
    ['val2', '0002'],
    ['val3', '0003']
  ];
  const at = if_empty(away_team);

  const collection = [menu, ht, [], at];
  const output = Array(Math.max(...collection.map((a) => a.length)))
    .fill()
    .map((_, i) => collection.flatMap((a) => a[i]));

  Logger.log(output)
}

But as you can see, index 0 has 6 values and the others have only 5:

[
  [abcd, null, null, null, val1, 0001],
  [1234, null, null, val2, 0002],
  [null, null, null, val3, 0003]
]

But I need that regardless of where values are missing, they must always be aligned with 6 values each:

[
  [abcd, null, null, null, val1, 0001],
  [1234, null, null, null, val2, 0002],
  [null, null, null, null, val3, 0003]
]

What should I readjust in my code to get around this problem?

I notice that the cause of this is in the 2D arrays that when they don't have values, they only generate 1 empty value instead of 2 empty values as expected by me.

Modification points:

• In your script, for example, the value of let collection = [menu, ht, [], at]; is [[["abcd"],["1234"]],[[null,null]],[],[["val1","0001"],["val2","0002"],["val3","0003"]]]. In this case, Math.max(...collection.map((a) => a.length)) is 3.
• When your script of const output = Array(Math.max(...collection.map((a) => a.length))).fill().map((_, i) => collection.flatMap((a) => a[i])); is run, at collection.flatMap((a) => a[i])), when i is 0, ["abcd"], [null,null], null, ["val1","0001"] are used. By this, 6 elements are included.
• When your script of const output = Array(Math.max(...collection.map((a) => a.length))).fill().map((_, i) => collection.flatMap((a) => a[i])); is run, at collection.flatMap((a) => a[i])), when i is 1, ["1234"], null, null, ["val2","0002"] are used. By this, 5 elements are included.
  • I thought that this might be the reason for your issue.

If my understanding is correct, I thought that in your script, it might be required to expand collection of let collection = [menu, ht, [], at]; to the same length for each element.

When these points are reflected in your script, it becomes as follows.

Modified script:

function if_empty(the_list) {
  if (the_list.length > 0) {
    return the_list
  } else {
    return [[null, null]]
  }
}

function group_arrays() {
  const menu = [
    ['abcd'],
    ['1234']
  ];

  const home_team = [];
  const ht = if_empty(home_team);

  const away_team = [
    ['val1', '0001'],
    ['val2', '0002'],
    ['val3', '0003']
  ];
  const at = if_empty(away_team);

  // --- I modified below script.
  let collection = [menu, ht, [], at];
  const maxLen = Math.max(...collection.map((a) => a.length));
  collection = collection.map(a => a.length != maxLen ? [...a, ...Array(maxLen - a.length).fill([...Array(a[0] ? a[0].length : 0)].fill(null))] : a);
  // ---

  const output = Array(Math.max(...collection.map((a) => a.length)))
    .fill()
    .map((_, i) => collection.flatMap((a) => a[i].length == 0 ? null : a[i]));

  console.log(output)
}

group_arrays();

• In this modification, in my modified script, [[["abcd"],["1234"]],[[null,null]],[],[["val1","0001"],["val2","0002"],["val3","0003"]]] is converted to [[["abcd"],["1234"],[null]],[[null,null],[null,null],[null,null]],[[],[],[]],[["val1","0001"],["val2","0002"],["val3","0003"]]]. By this, your expected values are retrieved.

Testing:

When the above script is run, you can see the following value at the log.

[
  ["abcd",null,null,null,"val1","0001"],
  ["1234",null,null,null,"val2","0002"],
  [null,null,null,null,"val3","0003"]
]