JavaScript - merge two sorted arrays in optimal way

In this short article, we would like to show how to merge two sorted arrays in an optimal way in JavaScript.

The below solution:

• requires sorted arrays on input,
• has O(n1 + n2) complexity.

Practical example:

// ONLINE-RUNNER:browser;

const mergeArrays = (a, b) => {
	const result = Array(a.length + b.length);
	let i = 0, j = 0, k = 0;
    while (i < a.length && j < b.length) {
		result[k++] = (a[i] < b[j] ? a[i++] : b[j++]);
    }
    while (i < a.length) {
        result[k++] = a[i++];
	}
    while (j < b.length) {
        result[k++] = b[j++];
	}
  	return result;
};


// Usage example:

const a = [1, 2, 4];
const b = [3, 5, 6];

const result = mergeArrays(a, b);

console.log(result);  // [1, 2, 3, 4, 5, 6]

See also

1. TypeScript - merge two sorted arrays in optimal way