Merge two sorted arrays in Javascript

In this blog we are writing program to merge two sorted arrays in javascript.

Problem :  Given two sorted arrays, merge them into a new array that is also sorted.

Input: arr1[] = { 1, 3, 4, 5}, arr2[] = {2, 4, 6, 8}

Output: arr3[] = {1, 2, 3, 4, 4, 5, 6, 8}

We will use Greedy Approach to write this program with efficient technique.

function mergeTwo(arr1, arr2) {
  let merged = [];
  let index1 = 0;
  let index2 = 0;
  let current = 0;

  while (current < (arr1.length + arr2.length)) {
      let unmerged1 = arr1[index1];
      let unmerged2 = arr2[index2];

      // if next comes from arr1
      if (unmerged1 < unmerged2) {
          merged[current] = unmerged1;
          index1++;

      // if next comes from arr2
      } else {
          merged[current] = unmerged2;
          index2++;
      }

      current++;
  }
const arr1 = [3, 5, 6, 10, 11, 20];
const arr2 = [1, 2, 7, 8, 15, 19];
mergeTwo(arr1, arr2);

Time Complexity : O(n)

Space Complexity: O(n)

In Javascript we can also use inbuilt functions to merge two arrays as show below:

function mergeTwo(arr1, arr2) {
  let result = [...arr1, ...arr2];
  return result.sort((a,b) => a-b);
}

const arr1 = [3, 5, 6, 10, 11, 20];
const arr2 = [1, 2, 7, 8, 15, 19];

mergeTwo(arr1, arr2); 

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