ECS-with-composition-and-types.ts

let _id = 0
const id = () => {
  _id++
  return _id
}

type Entity<Components = {}, Methods = {}> = {
  id: number
} & Components &
  Methods

interface NameComponent {
  name: string
}
interface WithName {
  components: { name: NameComponent }
}
const nameComponent = (name: string): NameComponent => {
  return { name }
}

interface JumpComponent {
  power: number
}
interface WithJump {
  components: { jump: JumpComponent }
}
const jumpProto = { _name: 'jump' }
const jumpComponent = (power: number = 3): JumpComponent => {
  return {
    power
  }
}

interface CanJump {
  jump: typeof jump
}
function jump(this: Entity<WithName & WithJump>) {
  console.log(
    this.components.name + ' jumped! This high: ' + this.components.jump.power
  )
}

type Rabbit = Entity<WithName & WithJump, CanJump>

const rabbit = (name: string): Rabbit => {
  return {
    id: id(),
    components: {
      name: nameComponent(name),
      jump: jumpComponent()
    },
    jump
  }
}

const john = rabbit('john')

john.jump()