geo_example.js

var MongoClient = require('mongodb').MongoClient;
var async = require('async');

var collection;
var db;
var resultsLimit = 2;

async.series([
    // open connection to local MongoDB server
    function(cb) {
        MongoClient.connect('mongodb://127.0.0.1:27017/test', function(err, db_in) {
            if (err) return cb(err);
            db = db_in;
            return cb();
        });
    },
    // add a list of items with coordinates
    function(cb) {
        collection = db.collection('geo_test');
        cb();
    },
    // create a geospatial index
    function(cb) {
        collection.createIndex({ loc : '2dsphere' }, function(err) {
            if (err) {
                console.error(err.stack);
                return cb(err);
            }
            return cb();
        });
    },
    // add items into the collection
    function(cb) {
        addItems(cb);
    },
    // find all items in the collection, within 5 miles of my location
    // at The Beacon
    function(cb) {
        // Note: here the coordinates are [ longitude, latitude ]
        var qry  = {
            loc: {
                $near: {
                    $geometry: {
                        type: 'Point',
                        coordinates: [-122.393868, 37.777151]
                    },
                    $maxDistance: 8046.72
                }
            }
        };
        collection.find(qry, {limit: resultsLimit}).toArray(function(err, results) {
            if (err) return cb(err);
            return cb(null, results);
        });
    },
    // drop the collection (delete it)
    function(cb) {
        collection.drop(function(err) {
            if (err) return cb(err);
            return cb();
        });
    }],
    // completion function & error handler
    function(err, results) {
        db.close();
        if (err) {
            console.error(err.stack);
            return;
        }
        // 4th index is where the query results are
        for (var i=0; i<results[4].length; i++) {
            console.log(i+1, results[4][i].name);
        }
    }
);

function setObj(obj) {
    obj.loc = { type: 'Point', coordinates: [ obj.lon, obj.lat ] };
    delete obj.lat;
    delete obj.lon;
    return obj;
}

// I know MongoDB is async and coordination is not needed, but ...
// I like known when all methods had an async cb triggered.
function addItems(cb) {
    async.map([
        { lat: 37.777151, lon: -122.393868, name: 'The Beacon'},
        { lat: 37.790130, lon: -122.394781, name: '199 Fremont'},
        { lat: 37.795743, lon: -122.393622, name: 'The Ferry Building'},
        { lat: 37.803220, lon: -122.257826, name: 'Lake Merit, Oakland'},
        { lat: 37.331555, lon: -121.887166, name: 'San Jose Tech Museum'},
        { lat: 36.964301, lon: -122.018511, name: 'Santa Cruz Boardwalk'},
    ],
    // iterator
    function (item, cb) {
        var obj = setObj(item);
        collection.insert(obj, function(err, docs) {
            return cb(err, docs);
        });
    },
    function(err) {
        if (err) {
            console.error(err.stack);
            collection.drop(function(err) {
                if (err) return cb(err);
                return cb();
            });
            return;
        }
        return cb();
    });
}