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Composition

Composition helpers wrap other actions without subclassing. They implement the same Action interface, so you can nest them arbitrarily and pass the result to entity.runAction().

Minimal example​

Runnable sample: website/snippets/actions/composition.ts.

import { moveBy, rotateBy, sequence, parallel, repeat, repeatForever, delay } from '@zylem/game-lib/actions';

patrol.runAction(
	repeat(
		sequence(
			parallel(
				moveBy({ x: 3, duration: 1500 }),
				rotateBy({ y: 90, duration: 1500 }),
			),
			delay(250),
			moveBy({ x: -3, duration: 1500 }),
		),
		3,
	),
);

spinner.runAction(repeatForever(rotateBy({ y: 360, duration: 2000 })));

Semantics​

HelperDurationCompletes when
sequence(...actions)Sum of child durationsLast child finishes
parallel(...actions)Max child durationAll children finish
repeat(action, times)action.duration × timesRan times cycles
repeatForever(action)InfinityNever

sequence forwards leftover delta time when a child finishes mid-frame, so chained short actions stay in sync with the frame clock.

Pitfalls​

  • repeatForever never sets done; use entity.clearActions() or keep it on a dedicated entity you destroy.
  • Empty sequence() completes immediately.
  • parallel with mixed zero-duration and long-duration children still waits for the longest child.

API reference​