const a = [
[1, 2, 3],
['a', 'b', 'c'],
[4, 5, 6],
['d', 'e', 'f'],
[7, 8, 9],
];
for (let i = 0; i < a.length; i++) {
for (let k = 0; k < a[i].length; k++) {
console.log(a[i][k]);
}
}
const a = [
[1, 2, 3],
['a', 'b', 'c'],
[4, 5, 6],
['d', 'e', 'f'],
[7, 8, 9],
];
console.log(a.reduce((acc, el) => [...acc, el[0]], []));