Calculate the midpoint between two pairs of (x,y) points

Destructure the array to get x1, y1, x2 and y2. Calculate the midpoint for each dimension by dividing the sum of the two endpoints by 2.

const midpoint = ([x1, y1], [x2, y2]) => [(x1 + x2) / 2, (y1 + y2) / 2];

// EXAMPLES
midpoint([2, 2], [4, 4]); // [3, 3]
midpoint([4, 4], [6, 6]); // [5, 5]
midpoint([1, 3], [2, 4]); // [1.5, 3.5]

Source

https://www.30secondsofcode.org/js/s/midpoint