minor performance upgrade

engine/lib/MapArray.ts

@@ -0,0 +1,37 @@
+import type { Box } from "#/engine/Box.ts";
+
+export default class MapArray<K, V> {
+	map: Map<K, Box<V>>;
+	array: Array<[K, Box<V>]>;
+
+	constructor(iterable?: Iterable<[K, Box<V>]>) {
+		this.map = new Map(iterable);
+		this.array = iterable ? [...iterable] : [];
+	}
+
+	delete(key: K): void {
+		if (this.map.delete(key)) {
+			this.array[this.array.findIndex((e) => e[0] === key)] =
+				this.array[this.array.length - 1];
+			this.array.pop();
+		}
+	}
+
+	set(key: K, value: Box<V>): void {
+		if (this.map.has(key)) {
+			this.array.find((e) => e[0] === key)![1] = value;
+		} else {
+			this.array.push([key, value]);
+		}
+
+		this.map.set(key, value);
+	}
+
+	get(key: K): Box<V> | undefined {
+		return this.map.get(key);
+	}
+
+	entries(): Array<[K, Box<V>]> {
+		return this.array;
+	}
+}

engine/lib/MapProxy.ts

@@ -1,25 +0,0 @@
-import type { Box } from "#/engine/Box.ts";
-
-export default class MapProxy<K, V> {
-	map: Map<K, Box<V>>;
-
-	constructor(iterable?: Iterable<readonly [K, Box<V>]>) {
-		this.map = new Map(iterable);
-	}
-
-	get(key: K): Box<V> | undefined {
-		return this.map.get(key);
-	}
-
-	entries(): MapIterator<[K, Box<V>]> {
-		return this.map.entries();
-	}
-
-	keys(): MapIterator<K> {
-		return this.map.keys();
-	}
-
-	values(): MapIterator<Box<V>> {
-		return this.map.values();
-	}
-}