TypeScript(JavaScript)でArrayのtranspose(転置・行列入れ替え)をする

の行列を入れ替えたい時ってありますよね。

const table = [
  ['www.apple.com', 'www.apple.com'],
  ['www.amazon.com', 'www.amazon.com', 'www.amazon.com'],
  ['www.google.com'],
].sort((a, b) => b.length - a.length);

table[0]
.map((_, idx) => table.map (row => row[idx]));

undefinedが嫌な時もありますよね。

const table = [
  ['www.apple.com', 'www.apple.com'],
  ['www.amazon.com', 'www.amazon.com', 'www.amazon.com'],
  ['www.google.com'],
].sort((a, b) => b.length - a.length);

table[0]
.map((_, idx) => table.map (row => row[idx]))
.map(row => row.filter(v => v));

まとめると

transpose = <T>(table: T[][]): T[][] => {
    return table
        .sort((a, b) => b.length - a.length)[0]
        .map((_, idx) => table.map(row => row[idx]))
        .map(row => row.filter(v => v));
}

via https://qiita.com/kznr_luk/items/790f1b154d1b6d4de398