I am looking for a function that returns a point (lat, long) between two points (where I also specify their lat, long) and that point is based on a distance percentage.
Assuming the coordinate is a decimal number. You can use this equation.
function midpoint(lat1, long1, lat2, long2, per) { return [lat1 + (lat2 - lat1) * per, long1 + (long2 - long1) * per]; }
Return a new desired coordinate of [lat, long], based on the percentage (such as per=0.2 for 20%).