JavaScript Design Patterns - Behavioral - Strategy

The strategy pattern defines a family of algorithms, encapsulates each one, and makes them interchangeable.

In this example, We have a set of discounts that can be applied to a shopping cart. We can pass the function that we will apply to the constructor and, in that way, change the amount discounted.

class ShoppingCart {
  constructor(discount) {
    this.discount = discount;
    this.amount = 0;
  }

  checkout() {
    return this.discount(this.amount);
  }

  setAmount(amount) {
    this.amount = amount;
  }
}

function guest(amount) {
  return amount;
}

function regular(amount) {
  return amount * 0.9;
}

function premium(amount) {
  return amount * 0.8;
}

export { ShoppingCart, guest, regular, premium };

A complete example is here 👉 https://stackblitz.com/edit/vitejs-vite-tygwh3?file=strategy.js

Conclusion

Use this pattern when you have a lot of similar classes that only differ in how they execute some behavior.

I hope you found it helpful. Thanks for reading. 🙏

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