Finding zip codes within the radius of a given address using SimpleGeo (with JS!)

simplegeo_zips.js

$(document).ready(function() {
    
    simplegeo_key = 'TOKEN';
    
    var places_client = new simplegeo.Places12Client(simplegeo_key);
    var context_client = new simplegeo.ContextClient(simplegeo_key);
    
    // Given an address and radius (and the SimpleGeo client), returns
    // a comma-separated list of zip codes within that radius.
    function get_nearby_zips(address, radius, places_client, callback) {        
        var location = {
            lon: 0,
            lat: 0
        };
        
        var something = context_client.getContextFromAddress(address, function(err, data) {
            if(err) {
                // Handle the error
                return false;
            } else {
                location.lat = parseFloat(data.query.latitude);
                location.lon = parseFloat(data.query.longitude);
                
                var pi = Math.PI;
                var rads = pi / 180;
                var degs = 180 / pi;
        
                var lat = location.lat * rads;
                var lon = location.lon * rads;
        
                var earths_radius = 6372.8;
        
                var distance = Math.sqrt(2 * Math.pow(radius,2)); // Find the hypotenuse
                distance = distance * 1.609344; // Convert to kilometers
        
                var ne_bearing = 45 * rads;
                var sw_bearing = 225 * rads;
        
                var sw_lat_rad = Math.asin(Math.sin(lat) * Math.cos(distance/earths_radius) +
                    Math.cos(lat) * Math.sin(distance/earths_radius) * Math.cos(ne_bearing));
                var sw_lat = sw_lat_rad * degs;
                
                var sw_lon_rad = lon + Math.atan2(Math.sin(ne_bearing) * Math.sin(distance/earths_radius) *
                    Math.cos(lat), Math.cos(distance/earths_radius) - Math.sin(lat) * Math.sin(sw_lat_rad));
                var sw_lon = sw_lon_rad * degs;
        
                var ne_lat_rad = Math.asin(Math.sin(lat) * Math.cos(distance/earths_radius) +
                    Math.cos(lat) * Math.sin(distance/earths_radius) * Math.cos(sw_bearing));
                var ne_lat = ne_lat_rad * degs;
        
                var ne_lon_rad = lon + Math.atan2(Math.sin(sw_bearing) * Math.sin(distance/earths_radius) *
                    Math.cos(lat), Math.cos(distance/earths_radius) - Math.sin(lat) * Math.sin(ne_lat_rad));
                var ne_lon = ne_lon_rad * degs;
        
                url = 'https://api.simplegeo.com/1.0/context/' + sw_lat + ',' + sw_lon + ',' + ne_lat + ',' + ne_lon;
                url += '.json?features__category=Postal+Code&token=' + simplegeo_key;
    
                $.getJSON(url, function(data) {
                    var bbox_zips = [];
                    $.each(data.features, function(k, v) {
                        bbox_zips[k] = v.name;
                    });
                    callback(bbox_zips.join(","));
                });
            }
        });
    }
    
    get_nearby_zips("444 W Main St, Lock Haven, PA", 10, places_client, function(zips) {
        console.log(zips);
    });

});