Change Detection

Change detection is very difficult to do performantly. Javelin does not currently implement a change detection algorithm that automatically watches component mutations. The only way to fit in potentially hundreds of thousands of tracked changes per tick is to write changes to a cache and decide what to do with them later.

Tracking Changes#

@javelin/ecs exports a function named observe which provides the means to track changes made to a component. observe accepts a component and returns a Proxy instance. This proxy will intercept any mutations made to any of a component's supported data structures, inlcuding structs, objects, arrays, sets, and maps.

import { component, observe } from "@javelin/ecs"
const position = component(Position)
const positionObserved = observe(position)

In the above example, positionObserved is a proxy which behaves identically to the original component. When the component is modified, Javelin will store the corresponding operations in an internal cache.

positionObserved.x = 1
positionObserved.y = 2

The only immediate use for observe is in conjunction with @javelin/net to serialize patches to be sent over the network. You will be able to produce your own patches and apply them to other components in a future version of Javelin.