flatten an array without using .flat();

Question

how can i flatten an array without using flat(). by 1 level?

so far i have this

function flatten(array) {
  let flattened = [];
  for (let i = 0; i < array.length; i++) {
    const current = array[i];
    for (let j = 0; i < current.length; j++) {
      flattened.push(current[j])
    }
  }
  return flattened
}

console.log(flatten([['foo', 'bar'], ['baz', 'qux']]));
// -> ["foo", "bar", "baz", "qux"]
flatten([[1], [2], 3, 4, [5]]);
// -> [1, 2, 3, 4, 5]
flatten([false, [true, [false]], [true]]);
// -> [false, true, [false], true]
flatten([]);
// -> []

and its crashing my memory

Answer 1

I hope this helps

var twoDimension = [[1], [2], 3, 4, [5]];

var plano = twoDimension.reduce((acc, el) => acc.concat(el), []);

console.log(plano);