Merge two sorted arrays to form a resultant sorted array in JavaScript

We are required to write a JavaScript function that takes in two sorted array of numbers. The function should merge the two arrays together to form a resultant sorted array and return that array.

For example −

If the two arrays are −

const arr1 = [2, 6, 6, 8, 9];
const arr2 = [1, 4, 5, 7];

Then the output array should be −

const output = [1, 2, 4, 6, 6, 7, 8, 9];

Example

The code for this will be −

const arr1 = [2, 6, 6, 8, 9];
const arr2 = [1, 4, 5, 7];
const mergeSortedArrays = (arr1 = [], arr2 = []) => {
   let m = arr1.length;
   let n = arr2.length;
   let currentIndex = m + n;
   const checkNum1HasLargerNumber = (a, b) => {
      if (a < 0) {
         return false;
      };
      if (b < 0) {
         return true;
      };
      return arr1[a] >= arr2[b];
   };
   m −= 1;
   n −= 1;
   while (currentIndex−−) {
      let hasNums1LargerNumber = checkNum1HasLargerNumber(m, n);
      arr1[currentIndex] = hasNums1LargerNumber ? arr1[m] : arr2[n];
      if (hasNums1LargerNumber) {
         m −= 1;
      } else {
         n −= 1;
      }
   };
};
mergeSortedArrays(arr1, arr2);
console.log(arr1);

Output

And the output in the console will be −

[
   1, 2, 4, 5, 6,
   6, 7, 8, 9
]