ECS

Simple ecs implementation, inspired by Unity3d ECS.

Getting Started

Installation

npm

npm install @vladnet/ecs

yarn

yarn add @vladnet/ecs

import { EntityManager, SystemManager } from "@vladnet/ecs";

Entities

Entities are managed by EntityManager. There are only two methods to work with entities, set and unset.

Set

Set without id creates new entity, set with id updates existed one.

console.log(em.length); // 0

// create new entity
let myEntity = em.set({
    name: "Petryk",
});
console.log(myEntity); // { id: "entity_1", name: "Petryk", }
console.log(em.length); // 1

// update existed one
myEntity = em.set({
    id: newEntity.id,
    name: "Vasylko",
}); 
console.log(myEntity); //{ id: "entity_1", name: "Vasylko", }
console.log(em.length); // 1

Unset

Just pass an entity id.

em.unset(myEntity.id);

Immutable

EntityManager never mutates your data.

// create new entity
const newEntity = em.set({
    name: "Petryk",
});
console.log(newEntity); // { id: "entity_1", name: "Petryk", }

// update existed one
const updatedEntity = em.set({
    id: newEntity.id,
    name: "Vasylko",
}); 
console.log(updatedEntity); //{ id: "entity_1", name: "Vasylko", }
console.log(newEntity === updatedEntity); // false

forEach/filter/find/toArray etc

EntityManager has few methods working in the same way as such methofs in Array: forEach, filter, find, some, every.

Sure thing, you can get plain array by em.toArray().

Observe

You could subscribe to set or unset events.

// on set
em.on(EEntityManagerEventTypes.set, (entity: IEntity) => {
    // entity was set (new or updated)
}, context /* `this` for listener */);

// on unset
em.on(EEntityManagerEventTypes.unset, (entity: IEntity) => {
    // entity was unset, do forget it and move forward
}, context /* `this` for listener */);

Systems

To manage you entities you should write a system. System is just an object having update method and optional start method.

interface ISystem {
    update: (em: EntityManager<IEntity>) => any;
    start?: (em: EntityManager<IEntity>) => any;
}

const em = new EntityManager();
const sm = new SystemManager(em);

// add a system
const id = sm.add({
    update(em) {
        em
            .filter(entity => entity.name === "Vasylko")
            .forEach(entity => {
                console.log(`Another one ${entity.name}!`);
            });
    }
});

// remove a system
sm.remove(id);

update will be run each time entity manager changes (both set or unset actions). It will not run again for system own changes. SystemManager saves timestamp when its EntityManager and systems were updated.

start will be run only once at SystemManager start.

Asynchronous

Systems are asynchronous, means you could update EntityManager at anytime and all other systems will update.

Start/Stop

// start all systems
sm.start();

// stop all systems
sm.stop();