Screeps Body class

readme.js

var body = new Body([CARRY, WORK, 2, MOVE]);
var spawn = Game.spawns.Spawn1;
if (spawn.energy >= body.cost()) {
	spawn.createCreep(body.longBody());
}

var creep = Game.creeps.John;
var body = new Body(creep.body);
console.log(creep, 'weight ratio: ', body.weight(creep.energy)); // useful for pathing

body.js

// Descriptor of a creep body
function Body(body) {
	this.body = body;
	this._isCreep = typeof body[0] === 'object';
	this._cost = undefined;
	this._weight = undefined;
}

_.assign(Body.prototype, {

	// How much energy is needed to build this body
	cost: function() {
		if (this._cost !== undefined) {
			return this._cost;
		}
		var mult = 1;
		var isCreep = this._isCreep;
		return this._cost = this.body.reduce(function(cost, desc) {
			var part = isCreep ? desc.type : desc;
			if (typeof part === 'number') {
				mult = part;
				return cost;
			} else {
				var tmp = cost + BODYPART_COST[part] * mult;
				mult = 1;
				return tmp;
			}
		}, 0);
	},

	// Weight ratio of this creep
	weight: function(energy) {
		if (this._weight !== undefined) {
			return this._weight;
		}
		var move = 0, len = 0;
		var mult = 1;
		var isCreep = this._isCreep;
		this._weight = this.body.forEach(function(desc) {
			var part = isCreep ? desc.type : desc;
			if (typeof part === 'number') {
				mult = part;
			} else {
				if (part === CARRY) {
					if (energy > 0) {
						var tmp = Math.ceil(Math.min(energy / CARRY_CAPACITY, mult));
						len += tmp;
						energy -= tmp * CARRY_CAPACITY;
					}
				} else if (part === MOVE) {
					move += mult;
				} else {
					len += mult;
				}
				mult = 1;
			}
		});
		return move ? Math.ceil(len / move) : undefined;
	},

	// Get the long-form body of this creep
	longBody: function() {
		var body = [];
		var mult = 1;
		var isCreep = this._isCreep;
		this.body.forEach(function(desc) {
			var part = isCreep ? desc.type : desc;
			if (typeof part === 'number') {
				mult = part;
			} else {
				for (var ii = 0; ii < mult; ++ii) {
					body.push(part);
				}
				mult = 1;
			}
		});
		return body;
	},
});