const array = [[[0], [1]], [[2], [3]], [[4], [5]]] 
const result = [];

function flattenArray(array) {
  for (let i = 0; i < array.length; i++) {
    if (typeof array[i] === "object") {
      flattenArray(array[i]);
    } else {
      result.push(array[i]);
    }
  }
}
flattenArray(array);