JSFiddle - React, Tailwind, and code Playground

JavaScript

var lat1=53.507651,lng1=10.046997,lat2=52.234528,lng2=10.695190;
function midpoint (lat1, lng1, lat2, lng2) {

lat1= deg2rad(lat1);
lng1= deg2rad(lng1);
lat2= deg2rad(lat2);
lng2= deg2rad(lng2);

dlng = lng2 - lng1;
Bx = Math.cos(lat2) * Math.cos(dlng);
By = Math.cos(lat2) * Math.sin(dlng);
lat3 = Math.atan2( Math.sin(lat1)+Math.sin(lat2),
Math.sqrt((Math.cos(lat1)+Bx)*(Math.cos(lat1)+Bx) + By*By ));
lng3 = lng1 + Math.atan2(By, (Math.cos(lat1) + Bx));

   return (lat3*180)/Math.PI .' '. (lng3*180)/Math.PI;
}

function deg2rad (degrees) {
    return degrees * Math.PI / 180;
};