Screeps hervester swarm - http://screeps.com

factory.js

var _ = require('lodash');

function countType(type) {
    return _.size(_.filter(Game.creeps, function (creep, creepName) {
        return creepName.split('_')[0] === type;
    }));
}

function build(spawn, type, attrNames) {
    var attrs = attrNames.map(function (name) {
        return Game[name.toUpperCase()];
    });
    
    var id = countType(type) + 1;
    spawn.createCreep(attrs, type + '_' + id);
}

module.exports = {
    worker: function (spawn) {
        build(spawn, 'worker', ['work', 'move', 'carry']);
    }
};

harvest.js

function harvest(creep) {
    var spawn = creep.pos.findNearest(Game.MY_SPAWNS);

    if (creep.energy < creep.energyCapacity) {
        var source = creep.pos.findNearest(Game.SOURCES);

        if (source) {
            creep.moveTo(source);
            creep.harvest(source);
        }
    }
    else {
        creep.moveTo(spawn);
        creep.transferEnergy(spawn);
    }
}

module.exports = harvest;

main.js

var harvest = require('harvest');
var factory = require('factory');
var _ = require('lodash');

_.mapValues(Game.creeps, harvest);

if (_.size(Game.creeps) < 10 && Game.spawns.Spawn1) {
    factory.worker(Game.spawns.Spawn1);
}