weak map gist

cache.ts

export class Cache<T extends object, K> {
	items = new WeakMap<T, K>()

	get<P extends T>(item: P, cb: (item: P) => K) {
		if (!this.items.has(item)) {
			this.items.set(item, cb(item))
		}
		return this.items.get(item)!
	}

	access(item: T) {
		return this.items.get(item)
	}

	set(item: T, value: K) {
		this.items.set(item, value)
	}

	has(item: T) {
		return this.items.has(item)
	}

	invalidate(item: T) {
		this.items.delete(item)
	}

	bust() {
		this.items = new WeakMap()
	}
}

gistfile1.ts

class Example {

  getOutline(shape) {
    const sides = 5 
        const ratio = 1
        const cx = w / 2
        const cy = h / 2
        const ix = (cx * ratio) / 2
        const iy = (cy * ratio) / 2
        const step = PI2 / sides / 2
        return Array.from(Array(sides * 2)).map((_, i) => {
          const theta = -TAU + i * step
          return new Vec2d(
            cx + (i % 2 ? ix : cx) * Math.cos(theta),
            cy + (i % 2 ? iy : cy) * Math.sin(theta)
          )
        })
  }

  outline(shape: T) {
    return outlines.get<T>(shape, (shape) => this.getOutline(shape))
  }