Flatten arbitrarily nested array.js

// The input, an arbitrarily nested array
const input = [
  [1, 2, 3],
  [4, 5, 6, [7, 8, [9, [10]]]]
];

/** 
 * Recursive function to be called on arrays
 * @param array The input array
*/
const flatten = (array) => (
  // Uses JavaScript's reduce() function to combine the elements into a single value
  array.reduce((acc, curr) => (
    // If the currently item (maybe the root array or a nested one) is an array itself,
    // apply the flatten() function to it and create a new array
    // by appending it to the elements in the accumulator using the spread operator
    Array.isArray(curr) ? [
      ...acc,
      ...flatten(curr),
    ] : [ // If not an array, just create a new array by appending it to the elements in the accumulator
      ...acc,
      curr,
    ]
  ), [])
);

const result = flatten(input); // [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]