Mongoose !

Let's start with mongoose !

Example : 

  1. // Include virtuals when converting documents to objects/JSON
  2. pizzaSchema.set("toObject", { virtuals: true });
  3. pizzaSchema.set("toJSON", { virtuals: true });

  5. // Virtual populate: connect Pizza -> Topping via Topping.pizzas (inverse relation)
  6. pizzaSchema.virtual("toppings", {
  7.   ref: "Topping",
  8.   localField: "_id",
  9.   foreignField: "pizzas",
  10.   justOne: false,
  11. });

  13. // Virtual total price (cents) includes toppings when `toppings` is populated
  14. pizzaSchema.virtual("totalPriceCents").get(function () {
  15.   // Compute total price from populated `toppings` only (no base pizza price)
  16.   if (
  17.     !this.toppings ||
  18.     !Array.isArray(this.toppings) ||
  19.     this.toppings.length === 0
  20.   )
  21.     return 0;
  22.   return this.toppings.reduce((acc, t) => acc + (t.priceCents || 0), 0);
  23. });

  25. pizzaSchema.virtual("totalPriceEur").get(function () {
  26.   return (this.totalPriceCents || 0) / 100;
  27. });

  29. export const Pizza = mongoose.model("Pizza", pizzaSchema);