axelf4/fowl

Javascript Pure Entity Component System

fowl

A truly lightweight Javascript Entity Component System

Usage

Components

Components are contructors that create objects of related data. The method fowl.registerComponents(...) has to be called once before instantiating components.

// A constructor for the Position component
var Position = function(x, y) {
	this.x = x;
	this.y = y;
};
fowl.registerComponents(Position); // Register the Position component for use with fowl

Entities

Creating entities

An EntityManager is necessary for dealing with entities. EntityManager.createEntity() will create an entity with zero components.

var em = new fowl.EntityManager();
var entity = em.createEntity();

Assigning components to entities

To add a component to an entity call EntityManager.addComponent(entity, component) with the entity and the component as arguments. Likewise does EntityManager.removeComponent(entity, component) remove a component.

em.addComponent(entity, new Position(10, 0));

Querying entities and their components

To iterate over the entities with e.g. the Position component you must first create a mask for the component types with EntityManager.getMask(componentTypes). Attn. You should allocate your masks at initialization only since they are costly to create.

var movementSystemMask = em.getMask([Position]);

Then, iterate over all entities and check whether they match the mask:

for (var entity = 0, length = em.count; entity < length; ++entity) {
	if (em.matches(entity, movementSystemMask)) {
		// Do stuff with `entity`
	}
}

To retrieve a component associated with an entity use EntityManager.getComponent(entity, component).

var position = em.getComponent(entity, Position);

Removing all entities

EntityManager.clear() removes all entities in play.