Calculate the largest latitude and longitude deltas needed to fit a set of points into based on an existing center point.

coordinate_delta.js

/**
 * Given a pre-defined set of coordinates as {latitude: ..., longitude: ...}
 * and a pre-defined center point with {latitude: ..., longitude: ...}
 * Find the zoom deltas needed for maps
 **

// Example:

var center = {latitude: 40.0348483, longitude: -73.00318473};
var points = [{latitude: ..., longitude: ...}, {latitude: ..., longitude: ...}, ...]
zoomDeltas(center, points); // => {latitudeDelta: ..., longitudeDelta: ...}

*/

var centerPoint = { latitude: 40.699878, longitude: -75.207924 };
var maxLatDelta = 0.0;
var maxLongDelta = 0.0;

var maxCoordinateDistance = function (point1, point2) {
  // finding "furthest distance" means finding
  // the maximum of the x/y deltas
  var latDelta  = Math.max(point1.latitude, point2.latitude) - Math.min(point1.latitude, point2.latitude);
  var longDelta = Math.max(point1.longitude, point2.longitude) - Math.min(point1.longitude, point2.longitude);
  
  return {
    latitudeDelta: latDelta,
    longitudeDelta: longDelta
  }
}

var zoomDeltas = function(centerPoint, coordinates) {
  for (var coordinate in coordinates) {
    var distanceFromCenter = maxCoordinateDistance(centerPoint, coordinate);
    maxLatDelta = Math.max(maxLatDelta, distanceFromCenter.latitudeDelta);
    maxLongDelta = Math.max(maxLongDelta, distanceFromCenter.longitudeDelta);
  }
  // maxLatDelta and maxLongDelta are now the furthest radial distance from
  // the center point, so multiply by 2 will give you the deltas you need
  // for zooming a map
  return {
    latitudeDelta: maxLatDelta * 2,
    longitudeDelta: maxLongDelta * 2
  };
};

you sir just saved my life