Merging nested arrays to form 1-d array in JavaScript

Problem

We are required to write a JavaScript function that takes in two nested arrays, arr1 and arr2, as the first and the second argument.

Our function should create and return a third array that contains all the elements of arr1 and arr2 but flattened to single dimension

For example, if the input to the function is −

const arr1 = [
   1, [
      2, [
         4, 5, [
            6
         ]
      ]
   ]
];
const arr2 = [
   11, 12, [
      16, 18, [
         19, 21, [
            23
         ]
      ]
   ]
];

Then the output should be −

const output = [1, 2, 4, 5, 6, 11, 12, 16, 18, 19, 21, 23];

Example

Following is the code −

 Live Demo

const arr1 = [
   1, [
      2, [
         4, 5, [
            6
         ]
      ]
   ]
];
const arr2 = [
   11, 12, [
      16, 18, [
         19, 21, [
            23
         ]
      ]
   ]
];
const flattenAndMerge = (arr1 = [], arr2 = []) => {
   const res = [];

   const flatten = (arr = []) => {
      for(let i = 0; i < arr.length; i++){
         if(Array.isArray(arr[i])){

            flatten(arr[i]);
         }else if(typeof arr[i] === 'number'){
            res.push(arr[i])
         };
      };
   };
   flatten(arr1);
   flatten(arr2);
   return res;
};
console.log(flattenAndMerge(arr1, arr2));

Output

Following is the console output −

[
   1, 2, 4, 5, 6,
   11, 12, 16, 18, 19,
   21, 23
]