Fix array with rows of different lengths by filling the empty elements with zeros in Javascript

Question

I have seen this question and from what I have worked on it contained the answer but unfortunately it used Python instead of Javascript. So I would like to ask an similar question.

I have an Javascript array which follows this format:

[[1,2,3],[4,5,6,7,8],[9,10]]

The function I am looking for should turn this array and pad all of them with zeros until they have all reached the max length (for this example as shown above it is 5). The function should output an array with this format:

[[1,2,3,0,0], [4,5,6,7,8],[9,10,0,0,0]]

ok. so what have you tried? show your code. – I wrestled a bear once. Aug 18 '20 at 12:54 — I wrestled a bear once., Aug 18 '20 at 12:54

score 1 · Answer 1 · answered Aug 18 '20 at 12:56

1

You can first find the longest subarray, and then create new subarrays of that length and fill them up with the original data:

function padArray(arr) {
  let length = Math.max(...arr.map(row => row.length));
  return arr.map(row => Array.from({length}, (_, i) => i < row.length ? row[i] : 0)); 
}

let arr = [[1,2,3],[4,5,6,7,8],[9,10]];
console.log(padArray(arr));

answered Aug 18 '20 at 12:56

trincot

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1

Can't we use .fill? – mplungjan Aug 18 '20 at 12:59
Sure, and spread or concat – trincot Aug 18 '20 at 13:15

score 0 · Answer 2 · answered Aug 18 '20 at 13:01

Calculate the remaining items and concat at the end.

const data = [[1,2,3],[4,5,6,7,8],[9,10]];

const result = data.reduce((r, c) => {
    const remainingLen = 5 - c.length;
    if (remainingLen > 0) {
        c = [].concat(c, new Array(remainingLen).fill(0));
    }
    
    r.push(c);
    return r;
}, []);

console.log(result);

Fix array with rows of different lengths by filling the empty elements with zeros in Javascript

2 Answers2