Reducing File Size

By default, the kontra export is the entire library. This means that by default Kontra is a bit large. However, Kontra has been written using ES Modules which means you can use a module bundler such as Rollup or esbuild to take advantage of tree-shaking. This will reduce the file size by only bundling the code you need.

// game.js
import { Sprite, GameLoop } from 'kontra';

let sprite = Sprite({
  x: 100,
  y: 100,
  dx: 2,
  width: 20,
  height: 40,
  color: 'red'
});

let loop = GameLoop({
  update() {
    sprite.update();
  },
  render() {
    sprite.render();
  }
});

loop.start();

# rollup
rollup game.js --format iife --file game.bundle.js

# esbuild
esbuild game.js --bundle --format=iife --outfile=game.bundle.js

Kontra Bundler Plugins

Kontra supports even more granular control over the file size if tree shaking is not enough. If you're looking to remove unused parts of the Sprite class, such as rotation or anchor, you can use a kontra bundler plugin to remove entire parts of the Sprite codebase. Just pass the functionality you want enabled and the bundler plugin will remove the rest.

// rollup.config.js
import kontra from 'rollup-plugin-kontra'

export default {
  entry: 'entry.js',
  dest: 'bundle.js',
  plugins: [
    kontra({
      gameObject: {
        // enable only velocity and rotation functionality
        velocity: true,
        rotation: true
      },
      vector: {
        // enable vector length functionality
        length: true
      },
      // turn on debugging
      debug: true
    })
  ]
}

Supported Plugins

• rollup-plugin-kontra
• esbuild-plugin-kontra

Available Options

Options are passed by nesting the option with the parent source. For example, to enable the image functionality of a sprite, you would pass sprite: { image: true }.

All options default to false, so only pass the options you wish to enable. Passing no options will result in a Sprite with just position, width, height, and color.

Note: Some of the more advance classes – such as Button or Grid – require some of the gameObject functionality to work properly. If you are using those, you will need to enable the group feature or they will not work.

gameObject Options:

Name	Functionality Enabled
acceleration	acceleration, ddx, ddy
anchor	anchor
group	children, parent, addChild, removeChild
opacity	opacity
rotation	rotation
scale	scaleX, scaleY, setScale()
ttl	ttl, isAlive
velocity	velocity, dx, dy

sprite Options:

Name	Functionality Enabled
animation	animations, playAnimation
image	image

text Options:

Name	Functionality Enabled
autoNewline	Setting a fixed with that automatically adds new lines to the text
newline	Support for new line characters (\n) in the text
rtl	Support for RTL languages
align	textAlign
stroke	strokeColor, lineWidth

tileEngine Options:

Name	Functionality Enabled
camera	sx, sy, add, remove
dynamic	setLayer, setTileAtLayer
query	layerCollidesWith, tileAtLayer
tiled	Support for resolving linked Tiled files (source, image)

vector Options:

Name	Functionality Enabled
angle	angle() (also enables length and dot)
clamp	clamp()
distance	distance()
dot	dot()
length	length()
normalize	normalize() (also enables length)
scale	scale()
subtract	subract()

General Options:

General options do not have a parent source and are passed as siblings to the other source options. For example, to enable debugging you would just pass debug: true.

Name	Functionality Enabled
debug	Turn on debugging information