Allergies

typescript/allergies/allergies.ts

@@ -0,0 +1,26 @@
+const allergenMap = {
+  eggs: 1,
+  peanuts: 2,
+  shellfish: 4,
+  strawberries: 8,
+  tomatoes: 16,
+  chocolate: 32,
+  pollen: 64,
+  cats: 128,
+} as const
+
+type Allergen = keyof typeof allergenMap
+
+export class Allergies {
+  constructor(private _allergenIndex: number) {}
+
+  public list(): Allergen[] {
+    return Object.entries(allergenMap)
+      .filter(([_, weight]) => (this._allergenIndex & weight) !== 0)
+      .map(([allergen]) => allergen as Allergen)
+  }
+
+  public allergicTo(allergen: Allergen): boolean {
+    return this.list().includes(allergen)
+  }
+}