Random Location Inside Circle

randomLocationInsideCircle.js

const RADIUS_EARTH = 6378000;   

const randomInsideCircle = (center, radius) => {
  const { lat, lng } = center;

  const [ a, b ] = [ Math.random(), Math.random() ].sort();

  const dx = b * radius * Math.cos((2 * Math.PI * a) / b);
  const dy = b * radius * Math.sin((2 * Math.PI * a) / b);

  const new_lat = lat + (dy / RADIUS_EARTH) * (180 / Math.PI);
  const new_lng = lng + ((dx / RADIUS_EARTH) * (180 / Math.PI)) / Math.cos((lat * Math.PI) / 180);

  return { lat: new_lat, lng: new_lng };
};