Add composite pattern example for solution

Author: leemhoon00

src/Composite/Book/index.ts

@@ -0,0 +1,44 @@
+export interface Component {
+  getPrice(): number;
+}
+
+class Product implements Component {
+  constructor(private name: string, private price: number) {}
+
+  getPrice(): number {
+    return this.price;
+  }
+}
+
+class Box implements Component {
+  private items: Component[] = [];
+
+  constructor(private name: string, private packagingCost: number) {}
+
+  addItem(item: Component) {
+    this.items.push(item);
+  }
+  removeItem(item: Component) {
+    this.items = this.items.filter((i) => i !== item);
+  }
+
+  getPrice(): number {
+    return (
+      this.packagingCost +
+      this.items.reduce((acc, item) => acc + item.getPrice(), 0)
+    );
+  }
+}
+
+const smallProduct = new Product("Small Product", 10);
+const smallBox = new Box("Small Box", 1);
+
+smallBox.addItem(smallProduct);
+
+const bigProduct = new Product("Big Product", 100);
+const bigBox = new Box("Big Box", 5);
+
+bigBox.addItem(bigProduct);
+bigBox.addItem(smallBox);
+
+console.log(bigBox.getPrice());