Map Reduce Alg to calculate the distance between nodes in mongo db

grap_map_reduce_test.js

var map = function() {
    if (this._id == 1) {
        emit(this._id, { distance: 0, name:'black' , childs: this.includes });
        this.includes.forEach(function(it) {
            emit(it, { distance: 1, name: 'gray', childs: [] })
        });
    } else {
        emit(this._id, { distance: -1, name: 'white', childs: this.includes });
    }
};

var reduce = function(key, values) {
    for (var idx in values) {
        if (values[idx].name === 'black') {
            return values[idx];
        }
    }
    var newEntry = {
        distance: 100000,
        name: 'black',
        childs: []
    };
    values.forEach(function(value) {
        if (value.name === 'gray' && value.distance < newEntry.distance) {
            newEntry.distance = value.distance;
        } else if (value.name === 'white') {
            newEntry.childs = value.childs;
        }
    });
    for(var idx in newEntry.childs) {
        emit(newEntry.childs[idx], { distance: newEntry.distance + 1, name: 'gray' , childs: [] });
    }
    return newEntry;
};

var finalize = function(key, value) {
    return {
        name: value.name,
        distance: value.distance
    }
};

var mongo = require('mongodb').MongoClient

var executeReduce = function(count) {
    mongo.connect('mongodb://localhost:27017/database', function(err, db) {
        var col = db.collection('graphtest');

        col.remove();
        for(var i = 1; i <= count; i++ ) {
            col.insert({ 
                _id : i,
                includes : [i-1]
                //includes : [Math.ceil(Math.random() * count), Math.ceil(Math.random() * count)]
            });
        }
        col.insert({ 
            _id : count,
            includes : [1, count, count]
        });
        setTimeout( function() {
            col.mapReduce(map, reduce, {
                out: 'graph_test_reduce', 
                finalize: finalize
            }).then(
                function(value) {
                    db.collection('graph_test_reduce').aggregate([{
                        $match: {
                            'value.distance': {
                                $gt: -1
                            }
                        }
                    }], function(err, result) {
                        console.log(result);
                        db.close();
                    });
                },
                function(err) {}
            );
        }, 2000);
    });
};

executeReduce(10);