Rook is a JavaScript library for creating games in the Entity-Component-System pattern. Rook is currently a work in progress. All contributions are welcome.

$ npm install --save rook-ecs

or

$ yarn add rook-ecs

After installing you can include the library in the source

import { Game } from 'rook-ecs'

console.log('Hurray!')

Alternatively, you might want to use an UMD build in the browser. To do so, grab the minified JavaScript file from here and add it to your site with a script tag.

In the browser all of the exports are available under the Rook global object.

<script src="rook-ecs.min.js"></script>
<script>
  console.log(Rook.Game)
</script>

First we declare the components. Components are just ids that correspond to some data. In JavaScript you don't need to declare anything, just use pure strings.

In TypeScript there is a special component function that creates type safe component ids.

import { component } from 'rook-ecs'

export interface Position {
  x: number,
  y: number,
}
export const Position = component<Position>('Position')

export interface Velocity {
  x: number,
  y: number,
}
export const Velocity = component<Velocity>('Velocity')

Having declared our components we can now use them in a system.

import { system, UpdateTick } from 'rook-ecs'
import { Position, Velocity } from './components'

export const move = system(UpdateTick, function (world, event) {
  for (const entity of world.query(Position, Velocity)) {
    const position = entity.get(Position)
    const velocity = entity.get(Velocity)
    position.x += velocity.x * event.deltaTime
    position.y += velocity.y * event.deltaTime
  }
})

And just like this, all our entities that have both the Position and Velocity components can now be updated with this system.

The only thing that's left is to start the game and create some entities.

import { start, gameClock } from 'rook-ecs'
import { Position, Velocity } from './components'
import { move } from './move'

function init (world) {
  world.create()
    .set(Position, { x: 0, y: 0 })
    .set(Velocity, { x: 10, y: 20 })
}

start([
  gameClock(),
  init,
  move,
])

Rook has first class TypeScript support since it is itself written with TypeScript. No special compiler options have to be specified for Rook to work, although we recommend using the strict: true setting.

Rook is currently a work in progress. All contributions are welcome.

• TypeScript Documentation
• T-Machine ECS Series